Multi-Transgenic Pigs for Diabetes Treatment

ABSTRACT

The present invention provides certain animals, and in particular porcine animals, tissue and cells derived from these, which lack any expression of functional alpha 1,3 galactosyltransferase (aGT) and express one or more additional transgenes which make them suitable donors for pancreatic islet xenotransplantation. Methods of treatment and prevention of diabetes using cells derived from such animals are also provided.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/857,514, filed Aug. 16, 2010, which is a non-provisional patentapplication claiming priority under 35 U.S.C. §119 to U.S. ProvisionalPatent Application No. 61/234,150, titled “Multi-Transgenic Pigs forDiabetes Treatment,” filed Aug. 14, 2009. The complete disclosure ofeach is hereby fully incorporated herein by reference.

FIELD OF THE INVENTION

The present invention provides certain donor animals, tissues and cellsthat are particularly useful for xenotransplantation therapies. Inparticular, the invention includes porcine animals, as well as tissueand cells derived from these, which lack any expression of functionalalpha 1,3 galactosyltransferase (aGT) and express one or more additionaltransgenes which make these animals suitable donors for pancreatic isletxenotransplantation. Methods of treatment and prevention of diabetesusing tissues and cells derived from such animals are also provided.

BACKGROUND OF THE INVENTION Diabetes

Insulin is a hormone produced by the pancreas that moves sugar from thebloodstream into the cells of the body, where it becomes an essentialenergy source. In mammals, insulin is synthesized in the pancreas withinthe beta cells (3-cells) of the islets of Langerhans (pancreaticislets). There are about one million islets in a healthy adult humanpancreas (about 1-2% of the total mass of the pancreas), which aredistributed throughout the organ

Diabetes is a disease state characterized by abnormally high levels ofsugar (hyperglycemia) in the blood, either because the body does notproduce enough insulin (Type 1 diabetes) or because the body cannotrespond to the insulin that is produced (Type 2 diabetes). Uncontrolled,hyperglycemia can lead to serious complications including blindness,heart disease, kidney disease and even death.

In the United States alone, more than 20 million people have diabetes.Type 2 diabetes (T2D) is by far the most common type, and is associatedwith lack of physical activity and obesity. According to statisticscompiled by the World Health Organization (WHO), in 2007, over 180million people world wide have diabetes, resulting in 2.9 million deaths(6% of total global mortality), and associated with a total economicburden of more than $230 billion.

Type 1 diabetes (T1D) is far less common than T2D. It is an autoimmunedisease in which the patient's own immune system destroys the body'sinsulin-producing pancreatic beta cells. Typically diagnosed at a youngage, it is a chronic disease that requiring life-long treatment.Treatment is generally in the form of insulin replacement therapy, whichis typically delivered by injection or pump. Successful insulinmanagement depends on how closely a given regimen can mimic normalphysiologic insulin release patterns. There are several different formsof insulin available, and the choice of a particular form/regime mayreflect that patient's preferences and ability to adhere to a particulartreatment regime. Despite advances in the pharmacology and delivery ofinsulin, achieving tight glycemic control using insulin replacementtherapy can be very demanding. As a result, many T1D patients stillexperience episodes of hyper- and hypo-glycemia and suffer long termcomplications as a result.

Given the burdens of insulin replacement therapy, therapeuticalternatives are highly desirable. Transplanted human pancreases(allografts) offer a potential cure for T1D patients. Sources includehuman donors that have recently deceased or living donors (partialpancreas transplant). The recipient's native pancreas is generally leftin place, and the donated pancreas is attached in a different location.Challenges include the risks inherent in any surgical procedure as wellthe possibility of rejection common to most transplanted organs.Rejection of the allograft pancreas may occur at any time from withinseconds (acute) to years (chronic) after transplantation. To avoidrejection, immunosuppressive drugs must be taken indefinitely. Thesedrugs can be difficult to tolerate, leave the patient at increased riskfor infectious disease and have also been linked to high blood pressure,kidney problems and liver disorders. The risks of transplantation andthe extended use of immunosuppressive drug therapy are uniquelyproblematic for diabetic patients (i.e., compared to other organtransplant recipients), as drug therapy generally remains an option,however undesirable. A 2003 study found that for patients withfunctioning kidneys, survival rates of patients who receivepancreas-only transplants were worse than the survival rates of patientswho manage their diabetes with conventional therapy (Venstrom et al.2003; 290:2817-2823). As a result, pancreas transplantation is normallyonly performed on individuals with type 1 diabetes with end-stage renaldisease.

Transplant of only the islet cells (versus the entire pancreas) providesa less invasive transplant-based alternative. Here, islets are isolatedfrom the donor pancreas and injected into the patient via a catheter tothe portal vein (i.e., no requirement for a major abdominal incision).The islets travel to the liver where they become fixed, taking overinsulin production and essentially turning the liver into a replacementpancreas. Early islet transplants had very low success rates, however,and patients remained insulin-independent for only short periods oftime. The major differences between the Edmonton Protocol and thoseearly islet transplant procedures was the use of a particularcombination of immunosuppressive drugs and transplant of islets frommore than one pancreas. Specifically, the Edmonton protocol uses acombination of immunosuppressive drugs that includes daclizumab,sirolimus and tacrolimus Daclizumab is given intravenously immediatepost-transplant and then discontinued. The patient is then givensirolimus and tacrolimus indefinitely.

Both whole pancreas and islet transplant procedures depend on a reliablesupply of human pancreas donors, which doesn't currently exist. Atpresent, only 3000 cadaver pancreases become available each year, farshort of those needed for the 2 million plus patients with T1D.

Gene therapy presents another therapeutic alternative. The introductionand expression of transgenes in human pancreatic islets to preventimmune rejection and improve proliferation and survival of islet graftshas been the focus of much research (review by McCabe et al., DiabetesMetab Res Rev. 2006 May-June; 22(3):241-52; Chuang et al., 2008; Martinet al., Endocr Dev. 2007; 12:24-32; Faideau et al., Diabetes. 2005December; 54 Suppl 2:S87-96). Transgene delivery via ex-vivotransduction of human islets has been investigated (Garcia-Ocana et al.,Journal of Biol Chem., 2003, 278:343-351; Li et al., TransplantationProceedings, 39:3436-3437). However, the immunomodulatory geneexpression in these systems was insufficient for long term diabeticcontrol as adenovirally infected islet grafts were rejected in about onemonth (see Sakata et al., Diabetes Research and Clinical Practice, 2008,80:352-359). In addition, adenoviral vectors used for gene therapy inhumans are limited in their capacity to deliver certain genes and havetriggered immune responses and even caused one death (Flotte, J. ofCellular Physiology, 2007, 213:301-305). The efficiency of alternative,non-viral gene delivery systems has been low and transient. Geneticmodification of human pancreatic cells has therefore failed toeffectively address the needs of T1D patients.

Xenotransplantation

Xenotransplantation (transplant of organs, tissues and cells from adonor of a different species) could effectively address the shortage ofhuman donor pancreases. Xenotransplants are also advantageously (i)supplied on a predictable, non-emergency basis; (ii) produced in acontrolled environment; and (iii) available for characterization andstudy prior to transplant.

Depending on the relationship between donor and recipient species, thexenotransplant can be described as concordant or discordant. Concordantspecies are phylogenetically closely related species (e.g., mouse torat). Discordant species are not closely related (e.g., pig to human).Pigs have been the focus of most research in the xenotransplanationarea, since the pig shares many anatomical and physiologicalcharacteristics with human. Pigs also have relatively short gestationperiods, can be bred in pathogen-free environments and may not presentthe same ethical issues associated with animals not commonly used asfood sources (e.g., primates).

Scientific knowledge and expertise in the field of pig-to-primatexenotransplantation has grown rapidly over the last decade, resulting inthe considerably prolonged survival of primate recipients of lifesavingporcine xenografts. (Cozzi et al., Xenotransplantation, 16:203-214.2009). Recently, significant achievements have been reported in thefield of islet xenotransplantation (Hering B J, et al., Nat Med,12:301-303. 2006; Cardona K, et al., Nat Med, 12:304306. 2006; GianelloP and Dufrane D., Xenotransplantation, 14: 441. 2007), and this progresshas prompted to may to suggest that islets, and not solid organs, may bethe first type of transplant in future clinical xenotransplantationtrials.

Genetic Modification

While advantageous in many ways, xenotransplantation also creates a morecomplex immunological scenario than allotransplantation. As such,considerable effort has been directed at addressing the immune barrierthrough genetic modification (van der Windt et al., Xenotransplantation.2007 July; 14(4):288-97, Cowan and D'Apice, Curr Opin Organ Transplant.2008 April; 13(2):178-83).

Xenograft rejection can be divided into three phases: hyperacuterejection, acute Immoral xenograft rejection, and T cell-mediatedcellular rejection. Hyperacute rejection (HAR) is a very rapid eventthat results in irreversible graft damage and loss within minutes tohours following graft reperfusion. It is triggered by the presence ofxenoreactive natural antibodies present within the recipient at the timeof transplantation. Humans have a naturally occurring antibody to thealpha 1,3-galactose (Gal) epitope found on pig cells. This antibody isproduced in high quantity and, it is now believed, is the principlemediator of HAR. (Sandrin et al., Proc Natl Acad Sci USA. 1993 December1; 90(23):11391-5, 1993; review by Sandrin and McKenzie, Immunol Rev.1994 October; 141:169-90). Initial efforts to genetically modify pigshave focused on removing the alpha 1,3-galactose (Gal) epitope from pigcells. In 2003, Phelps et al. (Science, 2003, 299:411-414) reported theproduction of the first live pigs lacking any functional expression ofαGT (GTKO), which represented a major breakthrough inxenotransplantation (see also PCT publication No. WO 04/028243 toRevivicor, Inc. and PCT Publication No. WO 04/016742 to ImmergeBiotherapeutics, Inc.). Subsequent studies have shown that organ graftsfrom GTKO pigs do not undergo HAR (Kuwaki et al., Nat Med. 2005 January;11(1):29-31, Yamada et al., Nat Med. 2005 January; 11(1):32-4). AlthoughGal-mediated HAR is now known to be a significant factor inxenotransplantation of whole organs.

It is not clear if HAR is also a critical factor in adult isletxenotransplantation as pure populations of pancreatic beta cells fromadult pigs do not express significant levels of the immunogenic Galepitope. Indeed, in one study, it was found that GTKO pig pancreaticislets were no less susceptible to destruction than wild type islets(Rood, et al. (2007) Transplantation 83:202-210). However, unlike adultislets, fetal and neonatal islets do express Gal.

Expression of complement regulators in xenotransplant tissue has beensuggested as a different strategy to combat HAR (Squinto, Curr OpinBiotechnol. 1996 December; 7(6):641-5). European patent 0495852 toImutran suggests associating xenograft tissues with recipient complementrestriction factors to reduce complement activation in the recipient(see also Diamond, et al., Transpl Immunol. 1995 December; 3(4):305-12).Transgenic pigs expressing human DAF (hDAF) and/or human CD59 (hCD59)have been reported (Byrne et al., Transplant Proc., 1996 April;28(2):758). CD46 has been expressed in pig cells using a minigene thatwas optimized for high ubiquitous expression and appears to protectporcine cells in a mouse transplantation model (Loveland et al.,Xenotransplantation, 2004, 11:171:183; McKenzie et al.,Xenotransplantation. 2003 November; 10(6):615-21). However, expressionof these factors has been variable and generally very low in pancreaticcells (see Bennet et al., Transplantation, 2001, 72:312-319).

Even where HAR is avoided, the xenograft undergoes a delayed form ofrejection, acute Immoral xenograft rejection (AHXR)—also referred to asdelayed xenograft rejection (DXR). It is generally thought to beinitiated by xeno-reactive antibodies, including non-Gal antibodies andsubsequent activation of the graft endothelium, the complement and thecoagulation systems (Miyagawa et al. Xenotransplantation, 2010, 1:11-25).

Although the threats presented by the Immoral response are critical withregard to the survival and function of vascularized grafts, the risk ofgraft damage by cellular mechanisms is also important. T-cell mediatedacute responses play an important role in xenotransplant rejection,although their role in transplantation of pancreatic islet cells has notbeen fully elucidated. Of several T cell costimulatory pathwaysidentified to date, the most prominent is the CD28 pathway and therelated cytoxic T-lymphocyte associated protein (CTLA4) pathway.

To date, much of the research on CTLA4-Ig as an immunosuppressive agenthas focused on administering soluble forms of CTLA4-Ig to a patient (seeU.S. Pat. No. 7,304,033; PCT Publication No. WO 99/57266; and Lui et al.J Immunol Methods 2003 277:171-183). To reduce the overallimmunosuppressive burden on a patient, transgenic expression of such aprotein has been suggested. Transgenic mice expressing CTLA4-Ig havebeen developed (Ronchese et al. J Exp Med (1994) 179:809; Lane et al. JExp Med. (1994) March 1; 179(3):819; Sutherland et al. Transplantation.2000 69(9):1806-12). In addition, PCT Publication No. WO 01/30966 toAlexion Pharmaceuticals, Inc. and PCT Publication No. WO 07/035213 toRevivicor discloses transgenic pigs expressing only the CTLA4-Igtransgene. See also Phelps et al., Xenotransplantation, 16(6):477-485.2009. Pigs expressing CTLA4Ig in brain tissue were produced, but highplasma expression was shown to cause negative effects (Martin, et al.(2005) Transg. Rsch. 14:373-84). There remains doubt as to whether longterm expression of immunosuppressive transgenes in ungulates raisessafety concerns either for the ungulate or for the recipient of anytissues from such an animal.

In addition to the cellular and Immoral immune responses, a significantchallenge associated with islet transplantation is the significant earlyloss of islet mass immediately after infusion of the transplanted isletsand contact with recipient blood, a phenomenon known as the immediateblood-mediated inflammatory response (IBMIR) (Bennet et al., Ups J MedSci 2000, 105:125-133). The addition of an anticoagulant transgene hasbeen suggested to prevent coagulation responses to xenografts (reviewedby Cowan, Xenotransplantation, 2007; 14:7-12). However, these reportshave focused on the reduction of coagulation associated with organtransplantation. In addition, production of anticoagulant-expressinganimals suitable for xenotransplantation has proven difficult due tobleeding phenotypes seen even in small mammals such as mice (see Dwyeret al. (2004) J Clin Invest 113: 1440-46). Furthermore, there is doubtas to whether anticoagulation is useful for preventing IBMIR. It hasbeen found that, in xenotransplant models, the use of complementdepletion or anticoagulation was insufficient to prevent IBMIR (Rood etal. 2007 Transplantation 83:202-210). Cabric, et al. (2006) Cell Transpl15:759-67 and (2007) Diabetes 56:2008-15) suggest that gene therapyapproaches are not appropriate for avoiding IBMIR in pancreatic isletsbecause they introduce new DNA into islets and are associated with arisk of inducing inflammatory or even adaptive immune responses, andtransduced islets showed an impaired glucose-stimulated insulin release.They instead suggest pretreatment of islet cells with agents such asheparin.

Although xenotransplantation of islets, particularly from porcinedonors, is an appealing alternative to the use of allografts because ofthe limited supply and quality of human pancreatic islets, majorobstacles remain. Both immediate and delayed immune responses and isletdestruction require potentially toxic cocktails of immunosuppressanttherapies. The production of genetically modified animals to addresscertain immune responses has been suggested, however this production hasmet with limited success because of toxicity associated with expressionof immunosuppressant in situ. There remains a need for improved animalsand tissues suitable for xenotransplantation therapies. In particular,there remains a need for improved animals and tissues to produce insulinproducing xenografts that will reduce diabetes in a patient withoutrequiring significant or long term immunosuppressive therapies.

SUMMARY OF THE INVENTION

The present invention provides genetically modified donor animals,tissues and cells that are particularly useful for xenotransplantationtherapies. More specifically, the genetically modified donor animalsserve as a source of tissues and cells that overcome significant Immoral(HAR and AHXR/DXR) and cellular immune responses (ACXR) as well as limitthe immediate blood-mediated inflammatory reaction (IBMIR), making themparticular useful for xenotransplantation therapy for diabetes, and inparticular type I diabetes, using a clinically relevantimmunosuppressant regimen, and with a reduced need for long termimmunosuppressant or anti-coagulant therapy.

The viable, genetically modified porcine animals of the presentinvention are characterized by globally reduced immune reactivity (i.e.,due to the lack of expression of functional alpha 1,3 galactosyltransferase (aGT)) as well as the expression of transgenes critical toovercome transplant rejection, selected from the group includinganti-coagulants, immunomodulators and cytoprotectants. Prior to thepresent invention, it was unknown whether these types of transgenes,which can cause the animal to be immuno-compromised and hemophilic,could be expressed in a single animal that would be able to be asuitable transplantation donor because it was expected that the animals'viability would be severely curtailed. The present inventors have foundthat such donor animals, tissues and cells can be obtained, inparticular when globally reduce immune reactivity due to lack ofexpression of functional alpha 1,3 galactosyltransferase (GTKO) iscombined with tissue-specific expression of certain transgenes.

In one embodiment of the present invention, porcine animals, tissues andcells are provided that lack any expression of functional alpha 1,3galactosyltransferase (GTKO) and that specifically express at least onetransgene in pancreatic tissue.

In a particular embodiment, the transgene specifically expressed inpancreatic tissue is at least one anti-coagulant. In another particularembodiment, the transgene specifically expressed in pancreatic tissue isat least one immunomodulator. In specific embodiment, the transgenespecifically expressed in pancreatic tissue is at least oneimmunosuppressant. In a further particular embodiment, the transgenespecifically expressed in pancreatic tissue is at least onecytoprotective transgene.

In another embodiment of the present invention, GTKO animals, tissuesand cells are provided that specifically express multiple transgenes inpancreatic tissue. In a particular embodiment, the multiple transgenesare selected from the group that includes anticoagulants,immunomodulators and cytoprotective transgenes.

In a particular embodiment, GTKO animals, tissues and cells are providedthat specifically express at least two transgenes in pancreatic tissue.In a specific embodiment, the at least two transgenes are bothanti-coagulants.

In a particular embodiment, GTKO animals, tissues and cells are providedspecifically express at least three transgenes in pancreatic tissue. Ina specific embodiment, the at least three transgenes include twoanti-coagulant transgenes and an immunosuppressant transgene.

In a further specific embodiment, GTKO animals, tissues and cells areprovided that lack any expression of functional alpha 1,3galactosyltransferase (GTKO) and that specifically express TFPI, CD39and CTLA4 in pancreatic tissue.

In a further embodiment of the present invention, porcine animals,tissues and cells are provided that lack any expression of functionalalpha 1,3 galactosyltransferase (GTKO) and that express at least onefirst transgene and at least one second transgene, wherein the secondtransgene is specifically expressed in pancreatic tissue.

In one embodiment, the at least one first transgene is animmunomodulator. In a particular embodiment, the at least one firsttransgene is a compliment inhibitor.

In another embodiment, the at least one first transgene is a complimentinhibitor and the at least one second transgene specifically expressedin pancreatic tissue is selected from the group that includes (i) ananti-coagulant; (ii) an immunosuppressive; and (iii) a cytoprotectant.

In one embodiment, porcine animals, tissues and cells are provided thatlack any expression of functional alpha 1,3 galactosyltransferase (GTKO)and expresses at least one compliment inhibitor and at least oneadditional transgene selected from the group consisting ofanti-coagulants, immunosuppressants and cytoprotectants.

In a specific embodiment, porcine animals, tissues and cells are providethat lack any expression of functional alpha 1,3 galactosyltransferase(GTKO) and expresses at least one compliment inhibitor and at least oneanti-coagulant. In a particular embodiment, the compliment inhibitor isCD46 and the at least one anticoagulant is selected from the group thatconsists of TFPI, CD39, hirudin, thrombomodulin and EPCR. In a furtherparticular embodiment, the at least one compliment inhibitor is CD46 andthe at least one additional transgene is an immunosuppressant, e.g.,CTLA4.

In a specific embodiment, procine animals, tissues and cells areprovided that lack any expression of functional alpha 1,3galactosyltransferase (GTKO) and further express at least one onecompliment inhibitor, at least one anticoagulant and at least oneimmunosuppressant. Optionally, the porcine animals, tissues and cellsalso express at least one cytoprotective transgene.

In one embodiment, the transgene is specifically expressed in pancreaticcells. In a particular embodiment, the transgene is specificallyexpressed in pancreatic islet cells. In a specific embodiment, thetransgene is specifically expressed in a beta cell. The expression canbe at any level, but in a specific embodiment, the expression is at ahigh level. In a particular embodiment, the cells are encapsulated.

An anticoagulant according to the present invention can be selected fromthe group that includes tissue factor pathway inhibitor (TFPI), hirudin,thrombomodulin, endothelial protein C receptor (EPCR), and CD39. In aparticular embodiment, the anticoagulant is TFPI. In another embodiment,the anticoagulant is CD39.

An immunomodulator according to the present invention can be acomplement inhibitor or an immunosuppressant. In specific embodiments,the immunomodulator is a complement inhibitor. The complement inhibitorcan be CD46 (or MCP), CD55, CD59 or CR1. In another specific embodiment,the immunomodulator is an immunosuppressant. The immunosuppressor can beCTLA4-1g. Other immunomodulators can be class II transactivator (CIITA)and mutants thereof, PDL1, PDL2, or tumor necrosis factor-a-relatedapoptosis-inducing ligand (TRAIL), Fas ligand (FasL, CD95L) CD47, knownas integrin-associated protein (CD47), HLAE, HLA-DP, HLA-DQ, HLA-DR.

The cytoprotective transgene according to the present invention can bean antiapoptotic, an anti-oxidant or an anti-inflammatory transgene. Incertain embodiments, the cytoprotective transgene is selected from thegroup that includes A20, HO-1, FAT-1, and soluble TNF-alpha receptor(sTNFR1).

In a specific embodiment, the present invention provides porcineanimals, tissues and cells are provided with at least the followinggenetic modifications: lack of expression of GT, expression of CD46 andpancreatic-specific expression of TFPI. In a particular embodiment, CD46is ubiquitously expressed.

In another specific embodiment, the present invention provides porcineanimals, tissues and cells are provided with at least the followinggenetic modifications: lack of expression of GT, expression of CD46,pancreatic-specific expression of TFPI, and pancreatic-specificexpression of CD39. In a particular embodiment, CD46 is ubiquitouslyexpressed.

In another specific embodiment, the present invention provides porcineanimals, tissues and cells are provided with at least the followinggenetic modifications: lack of expression of GT, expression of CD46,pancreatic-specific expression of TFPI, and pancreatic-specificexpression of CTLA4-1g. In a particular embodiment, CD46 is ubiquitouslyexpressed.

In a further specific embodiment, the present invention provides porcineanimals, tissues and cells are provided with at least the followinggenetic modifications: lack of expression of GT, expression of CD46,pancreatic-specific expression of TFPI, pancreatic-specific expressionof CD39, and pancreatic-specific expression of CTLA4-1g. In a particularembodiment, CD46 is ubiquitously expressed.

In another specific embodiment, the present invention provides porcineanimals, tissues and cells are provided with at least the followinggenetic modifications: lack of expression of GT, expression of CD46,expression of an cytoprotective transgene, pancreatic-specificexpression of TFPI, pancreatic-specific expression of CD39, andpancreatic-specific expression of CTLA4-1g. In a particular embodiment,CD46 is ubiquitously expressed.

In another specific embodiment, the present invention provides porcineanimals, tissues and cells are provided with at least the followinggenetic modifications: lack of expression of GT, expression of CD46,expression of an cytoprotective transgene, pancreatic-specificexpression of TFPI and pancreatic-specific expression of CD39. In aparticular embodiment, CD46 is ubiquitously expressed.

In one embodiment, a method is provided for treatment or prophylaxis ofdiabetes including administering the tissues or cells of the presentinvention to a host in need thereof In a particular embodiment, the hostis a diabetic host.

In one embodiment, the diabetic host is a diabetic primate. In aparticular embodiment, the host is a diabetic human. In a specificembodiment, the host is a human suffering from Type 1 diabetes (T1B).

In one embodiment, the tissue is porcine pancreas tissue. In anotherembodiment, the cells are pancreas-derived cells, whole islets, orisolated pancreatic islet cells. In a particular embodiment, the cellsare islets. In another particular embodiment, the pancreatic cells arebeta cells. In one embodiment, the pancreatic cells are adult cells. Inanother embodiment, the pancreatic cells are fetal or neonatal cells.

In one embodiment, a method is provided to treating or preventingdiabetes that includes administering islet cells isolated from porcineanimals of the present invention.

In an alternative embodiment, a method is provided to reduce the amountof insulin required by a diabetic host by administering the tissues orcells of the present invention to a diabetic host. In a particularembodiment, the host requires reduced or no exogenous insulin aftertreatment. In one embodiment, the host requires from about 5% to about25% less insulin after treatment. In another embodiment, the hostrequires from about 25% to about 50% less insulin after treatment. Inyet another embodiment, the host requires from about 50% to about 75%less insulin after treatment. In a still further embodiment, the hostrequires from about 75% to about 100% less insulin after treatment.

In a particular embodiment, after treatment, the host requires less than4 units of insulin/day, less than 3 units of insulin/day, less than 2,less than 2 units of insulin/day, or less than 1 unit of insulin/day. Inone embodiment, after treatment, the host requires no exogenous insulin.

In other embodiments, tissues or cells provided herein can be used inre-transplant procedures, such procedures may be necessary, for example,in certain embodiments, to maintain sufficient levels of islets tocontrol glycemia long-term.

In one embodiment of the present invention, a method is provided fortreatment or prophylaxis of diabetes including administering the tissuesor cells of the present invention to a host suffering from diabetes,wherein the host requires no or reduced immunosuppressive therapy afterthe treatment.

In one embodiment, the dose of immunosuppressive drug(s)/agent(s) is/arereduced compared to other methods. In a specific embodiment, the dosageof one or more of daclizumab, tacrolimus, and/or sirolimus is reducedcompared to dosages used in other methods of transplantation.

In another embodiment, the number of types of immunosuppressivedrug(s)/agent(s) is/are reduced compared to other methods.

In one embodiment, the duration of immunosuppression is shortenedcompared to other methods.

In another embodiment, lower or no maintenance immunosuppression is usedcompared to other methods.

In one embodiment, a method is provided for treatment or prophylaxis ofdiabetes including administering the tissues or cells of the presentinvention to a host suffering from diabetes, wherein the IEQ/kg(pancreatic islet equivalents per kg) requirements are reduced comparedto other methods. In another embodiment, the IEQ/kg is below 100,000. Ina further embodiment, the IEQ/kg is below 50,000. In one embodiment, theIEQ/kg is below 25,000. In another embodiment, the IEQ/kg is below10,000.

In a further embodiment, a method is provided for treatment orprophylaxis of diabetes including administering the pancreatic cells orislets of the present invention to a host suffering from diabetes,wherein the tissues or cells are administered by intraportal infusion.In a particular embodiment, islets are administered by intraportalinfusion. In one embodiment, the islets are administered into theintraperitoneal space, renal subcapsule, renal capsule, omentum, or viapancreatic bed infusion.

In another embodiment, a method is provided for treatment or prophylaxisof diabetes including administering the pancreatic cells or islets ofthe present invention to a host suffering from diabetes, wherein thetissues or cells are encapsulated. In one embodiment, the cells aremicroencapsulated. In an alternate embodiment, the cells aremacroencapsulated. In another embodiment, the cells are notencapsulated. In a particular embodiment, the cells are provided in theform of a thin planar sheet containing purified alginate and cells. In aspecific embodiment, the islets are microencapsulated, macroencapsulatedor provided as a thin planar sheet of containing purified alginate andislets.

In further embodiments, a method is provided for treatment orprophylaxis of diabetes including administering the tissues or cells ofthe present invention to a diabetic host, wherein after the transplantthe host has some or all functional transplanted cells. In oneembodiment, the host has more functional transplanted islets compared tothe number of functional transplanted islets present after performingother methods. In one embodiment, islet functionality is defined asbasal or stimulated porcine C-peptide greater than 0.3 ng/dl. In oneembodiment, islet functionality is defined as detectable porcineC-peptide in combination with a greater than 50% reduction of exogenousinsulin needs, wherein the C-peptide is produced from the transplantedmaterial. In a particular embodiment, 10, 20, 30, 40, 50, 60, 70, 80,90, 100% of the transplanted islets are functional.

In other embodiments, a method is provided for treatment or prophylaxisof diabetes including administering the tissues or cells of the presentinvention to a diabetic, wherein after the transplant the host canmaintain normoglycemia. In one embodiment, normoglycemia is maintainedfor at least 3 months. In another embodiment, normoglycemia ismaintained for at least 6 or at least 12 months.

In other embodiments, a method is provided for treatment or prophylaxisof diabetes including administering the tissues or cells of the presentinvention to a diabetic, wherein after the transplant the fasting andnon-fasting blood glucose levels (FBG and NFBG, respectively) of thehost are maintained at normal levels. In one embodiment, the normallevels should be maintained for at least 3 months. In anotherembodiment, the normal levels should be maintained for at least 6months. In another embodiment, the normal levels should be maintainedfor at least 12 months. In a particular embodiment, FBG can bemaintained from about 70 to about 100 mg/dL (3.9 to 5.5 mmol/L). Inanother embodiment, the FBG can be maintain from about 70 to about 130mg/DL. In another particular embodiment, NFBG can be maintained at lessthan about 200 mg/dL.

In one embodiment, after treatment, the host has a glycated hemoglobinlevel of less than about 8.0%. In another embodiment, after treatment,the host has a glycated hemoglobin level of less than about 6.5%.

In one embodiment, a method is provided for treatment or prophylaxis ofdiabetes including administering the tissues or cells of the presentinvention to a diabetic host, wherein the host successfully passes anintravenous glucose tolerance test post-transplant. In one embodiment,the test can be performed at 1, 3, 6 and/or 12 months post transplant.In another embodiment, the results of the test are successful ifsignificant response to glucose in the form of porcine C-peptide isdemonstrated in the absence of a significant response of non-humanprimate C-peptide.

In another embodiment, a method is provided for treatment or prophylaxisof diabetes including administering the tissues or cells of the presentinvention to a diabetic host suffering from diabetes, wherein the hostsuccessfully passes an arginine stimulation test post-transplant. In oneembodiment, the test can be performed at 1, 3, 6 and/or 12 months posttransplant. In another embodiment, the results of the test aresuccessful if significant response to glucose in the form of porcineC-peptide is demonstrated in the absence of a significant response ofnon-human primate C-peptide.

In one embodiment, a method is provided for treatment or prophylaxis ofdiabetes including administering the tissues or cells of the presentinvention to a diabetic host, wherein after the transplant donorC-peptide levels are detectable. In another embodiment, porcineC-peptide levels are about between about 0.3 and about 0.96. In onespecific embodiment, porcine C-peptide levels are about between about0.21 and about 0.63 (ng/ml).

In another embodiment, a method is provided for treatment or prophylaxisof diabetes including administering the tissues or cells of the presentinvention to a diabetic host, wherein post-transplant histologicalanalysis of the host is conducted. In one embodiment, the histologicalanalysis of the native pancreas after necropsy indicates reduced, in onenon-limiting example, none, insulin-positive beta cells. In a furtherembodiment, the histological examination of the liver or other site ofislet transplant indicates multiple viable insulin-positive cells.

In a further embodiment, a method is provided for treatment orprophylaxis of diabetes including administering the tissues or cells ofthe present invention to a diabetic host, wherein post-transplant thereare not numerous, or serious life-threatening, complications associatedwith one or more of the transplant procedure, the immunosuppressiveregime, tolerance inducing regime or the encapsulation of the islets.

Other embodiments of the present invention will be apparent to one ofordinary skill in light of the following description of the invention,the claims and what is known in the art.

DESCRIPTION OF FIGURES

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 is a representative figure of the vectors used in the invention.“pREV788” is the base vector; pREV790 is the base vector with a TFPI-CD4transgene; pREV792 is the base vector with a pCTLA4-Ig transgene; andpREV835 is the base vector with a CD39 transgene.

FIG. 2 shows images of pCTLA4-Ig protein expression in transgenic pigorgan lysates as detected by Western blot analysis under reduced anddenaturing conditions. Bands were detected with antibody specific forthe Ig portion of the fusion protein. 347-3 and 342-1 are reclones offetus 548/A3 and 340-2 is a nontransgenic animal (used as a negativecontrol).

FIG. 3 is images of cells stained with FITC-labeled anti-human TFPIantibody showing high levels of hTFPI observed in adult transgenic mousepancreas, with localized expression in islets. H&E staining showsrepresentative islet morphology.

FIG. 4 is images of fetal pancreas from 548/A3 stained with FITC-labeledanti-human TFPI Ab and FITC-labeled anti-human IgGi (which binds to thehuman Ig portion of the pCTLA4-1g), showing expression of TFPI andpCTLA4-1g.

FIG. 5 is images of pancreas from 2.5 month old piglet 347-3 (a redoneof 548/A3), stained with FITC-labeled anti-human TFPI Ab, andFITC-labeled antihuman IgGi (which binds to the human Ig portion of thepCTLA4-1g), showing expression of both the TFPI and pCTLA4-Igtransgenes. Staining for insulin shows a similar pattern to that of thetransgenes. Wild type pig and isotype controls are also shown.

FIG. 6 is images of pancreas from piglet 320-2, stained withFITC-labeled anti-human C1339, showing high expression of C1339.Staining for insulin is also shown.

FIG. 7 is images of pancreas from piglet 342-3, a redone of 548/A3stained with FITC-labeled anti-human C1346, showing high expression ofC1346.

FIG. 8 illustrates released phosphate levels in islets from pig 390-1compared to wildtype islets.

FIG. 9 is staining results for C1346, TFPI, CTLA4-1g, C1339, and insulinin pig 390-1

DETAILED DESCRIPTION OF THE INVENTION

There is increasing evidence that donor vascular endothelial cells,present in the islet grafts, play an important role in the formation ofnew blood vessels involved in revascularization of the islet tissue inthe recipients post-transplant (Linn et al., FASEB, (2003)17:881-883;Brissova et al., Diabetes (2004) 53:1318-1325; Johansson U, et al., AmJ. Transplant. (2005) 5:2632-2639; Nyqvist, et al., Diabetes, (2005)54:2287-2293). Some new vessels are lined with donor endothelial cells,while other vessels may be reconstituted as chimeras of donor andrecipient cells (Brissova et al., Diabetes (2004) 53:1318-1325). Withoutthe presence of viable donor endothelial cells, revascularization isdelayed and incomplete, resulting in ischemic injury and death of manyof the islets. Therefore, the present invention comprises pigs with theGTKO genetic background plus other transgenes towards improved outcomesin islet transplantation. Islets from GTKO pigs expressing othertransgenes specifically in pancreas, will provide significant protectionof the donor endothelial cells, and therefore of the islets.

A “transgene” is a gene or genetic material that has been transferredfrom one organism to another. Typically, the term describes a segment ofDNA containing a gene sequence that has been isolated from one organismand is introduced into a different organism. This non-native segment ofDNA may retain the ability to produce RNA or protein in the transgenicorganism, or it may alter the normal function of the transgenicorganism's genetic code. In general, the DNA is incorporated into theorganisms germ line. For example, in higher vertebrates this can beaccomplished by injecting the foreign DNA into the nucleus of afertilized ovum. When inserted into a cell, a transgene can be either acDNA (complementary DNA) segment, which is a copy of mRINA (messengerRNA), or the gene itself residing in its original region of genomic DNA.The transgene can be a genome sequence, in particular when introduced aslarge clones in BACs (bacterial artificial chromosomes) or cosmid.Transgene “expression” in the context of the present specification,unless otherwise specified, means that a peptide sequence from anon-native nucleic acid is expressed in at least one cell in a host. Thepeptide can be expressed from a transgene that is incorporated in thehost genome.

A “donor” is meant to include any non-human organism that may serve as asource of donor tissue or cells for xenotransplantation including, butnot limited to, mammals, birds, chickens, reptiles, fish, and insects.The donor may be in any stage of development, including, but not limitedto fetal, neonatal, young and adult. An “animal” is typically a mammal.A “mammal” is meant to include any non-human mammal, including but notlimited to pigs, sheep, goats, cattle (bovine), deer, mules, horses,monkeys, dogs, cats, rats, and mice. In one embodiment of the invention,genetically altered pigs and methods of production thereof are provided.The animals of the invention are “genetically modified” or “transgenic,”which means that they have a transgene, or other foreign DNA, added orincorporated, or an endogenous gene modified, including, targeted,recombined, interrupted, deleted, disrupted, replaced, suppressed,enhanced, or otherwise altered, to mediate a genotypic or phenotypiceffect in at least one cell of the animal, and typically into at leastone germ line cell of the animal. In some embodiments, animals may havethe transgene integrated on one allele of its genome (heterozygoustransgenic). In other embodiments, animals may have the transgene on twoalleles (homozygous transgenic).

The term “ungulate” refers to hoofed mammals. Artiodactyls are even-toed(cloven-hooved) ungulates, including antelopes, camels, cows, deer,goats, pigs, and sheep. Perissodactyls are odd toes ungulates, whichinclude horses, zebras, rhinoceroses, and tapirs. The term ungulate asused herein refers to an adult, embryonic or fetal ungulate animal.

The terms “porcine”, “porcine animal”, “pig” and “swine” are genericterms referring to the same type of animal without regard to gender,size, or breed.

The “cells” of the invention are derived from an animal. Although thecells can be derived from a mature animal, in some embodiments the cellis derived from a fetal or neonatal tissue. In particular embodiments ofthe invention, the cells, and especially the pancreatic islet cells, arederived from a transgenic porcine animal and in particular, a transgenicporcine that has grown to a sufficient size to be useful as an adultislet donor. In certain embodiments, the animals survive past weaningage. In specific embodiments, the animals are at least six months old.In certain embodiments, the animal survives to reach breeding age. Incertain embodiments, the animal is a porcine animal of at least 300pounds. In specific embodiments, the animal is a porcine sow and hasgiven birth at least one time.

“High” levels of expression are considered sufficient to provide aphenotype (detectable expression or therapeutic benefit). Typically a‘high’ level of expression is sufficient to be capable of reducing graftrejection including hyperacute rejection (HAR), acute Immoral xenograftrejection (AHXR), T cell-mediated cellular rejection and immediateblood-mediated inflammatory response (IBMIR). It was previously unknownwhether anticoagulant and immunosuppressive transgenes could beexpressed in pancreatic islet cells at levels capable of reducing thesetypes of rejection.

Transgenic Animals

In one embodiment, porcine animals, tissues and cells are provided thathave at least four genetic modifications. Such genetic modifications caninclude, without limitation, additions and/or deletions of genes,including knock-outs and knock-ins, as well as re-arrangements. In aparticular embodiment, porcine animals, tissues and cells are providedthat have at least four genetic modifications, wherein at least one, atleast two, at least three or four of the genetic modifications are transgenes and at least one, at least two, at least three or four of thetransgenes are ubiquitously expressed. In a particular embodiment,porcine animals, tissues and cells are provided that have at least fourgenetic modifications, wherein at least one genetic modification is aknockout.

In a particular embodiment, porcine animals, tissues and cells areprovided that have at least one gene knocked out and express at leastthree transgenes. In a specific embodiment, the at least one gene isknocked out by homologous recombination.

In one embodiment, porcine animals, tissues and cells are provided thathave at least five genetic modifications. Such genetic modifications caninclude, for example, additions and/or deletions of other genes,including knock-outs and knock-ins, as well as rearrangements. In aparticular embodiment, porcine animals, tissues and cells are providedthat have at least five genetic modifications, wherein at least one, atleast two, at least three, at least four or five of the geneticmodifications are transgenes and at least one, at least two, at leastthree, at least four or five of the transgenes are ubiquitouslyexpressed. In a particular embodiment, porcine animals, tissues andcells are provided that have at least five genetic modifications,wherein at least one genetic modification is a knock-out.

In a particular embodiment, porcine animals, tissues and cells areprovided that have at least one gene knocked out and express at leastfour transgenes. In a specific embodiment, the at least one gene isknocked out by homologous recombination.

In one embodiment, porcine animals, tissues and cells are provided thatlack any expression of functional alpha 1,3 galactosyltransferase (GTKO)and express at least one transgene in pancreatic tissue. In otherembodiments, GTKO animals, tissues and cells are provided which expressmultiple transgenes in pancreatic tissue. In particular subembodiments,the animals, tissues and cells express at least one immunomodulator. Incertain embodiments, the animals, tissues and cells express more thanone immunomodulator. In particular embodiments, GTKO animals, tissuesand cells are provided that express at least one immunomodulator and atleast one anti-coagulant transgene. In one embodiment, theimmunomodulator is an immunosuppressant. In an alternate embodiment, theimmunomodulator is a complement inhibitor. In a particular embodiment,expression of the immunomodulator is specific to the pancreas. In afurther particular embodiment, expression of the immunosuppressant isspecific to the pancreas. In a still further specific embodiment,expression of the compliment inhibitor is specific to the pancreas. Inother subembodiments, the animals, tissues and cells express at leastone anticoagulant. In certain embodiments, the animals, tissues andcells express more than one anticoagulant. In a particular embodiment,the expression of the anticoagulant is specific to the pancreas. In onesubembodiment, the animals, tissues and cells express at least onecytoprotective transgene. In another embodiment, the animals, tissuesand cells express more than one cytoprotective transgene. In oneembodiment, the transgene is specifically expressed in islets, in aparticular embodiment, specific expression in beta cells is provided.

In one embodiment, the present invention includes GTKO animals, tissueand cells that lack any expression of functional alpha 1,3galactosyltransferase (GTKO) and expresses at least one complimentinhibitor and at least one additional transgene selected from the groupconsisting of anti-coagulants, immunosuppressants and cytoprotectants.In a particular embodiment, the expression of the at least oneadditional transgene is specific to the pancreas.

In a specific embodiment, GTKO animals, tissues and cells are providedthat express at least one compliment inhibitor (e.g., CD46) and at leastone anti-coagulant (e.g., TFPI).

In another specific embodiment, GTKO animals, tissue and cells areprovided that express at least one compliment inhibitor (e.g., CD46) andat least two anticoagulants (e.g., TFIP and CD39).

In another specific embodiment, GTKO animals, tissues and cells areprovided that express at least one compliment inhibitor (e.g., CD46) andat least one immunosuppressant (e.g., CTLA4).

In a still further specific embodiment, GTKO animals, tissues and cellsare provided that express at least one compliment inhibitor (e.g., CD46)and a cytoprotective trans gene (e.g., A20).

In certain embodiments, GTKO animals, tissues and cells are providedthat express at least one immunosuppressant, at least one complementinhibitor and at least one anticoagulant transgene. In an furtherparticular embodiment, GTKO animals, tissues and cells are provided thatexpress at least one immunosuppressant, at least one complementinhibitor and at least two anticoagulant transgenes. In a specificembodiment, GTKO animals, tissues and cells are provided that express atleast one immunosuppressant, at least one complement inhibitor and atleast one anticoagulant transgenes, wherein expression of the at leastone immunosuppressant and the at least one anticoagulant transgenes isspecific to the pancreas. In yet another specific embodiment, GTKOanimals, tissues and cells are provided that express at least oneimmunosuppressant, at least one complement inhibitor and at least twoanticoagulant transgenes, wherein expression of the at least oneimmunosuppressant and the at least two anticoagulant transgenes isspecific to the pancreas. In one embodiment, the transgene isspecifically expressed in islets, in a particular embodiment, specificexpression in beta cells is provided.

In one embodiment, GTKO animals, tissues and cells are provided thatexpress at least one immunomodulator, at least one anticoagulant and atleast one cytoprotective transgene. In a further embodiment, GTKOanimals, tissues and cells are provided that express at least oneimmunosuppressant, at least one complement inhibitor, at least oneanticoagulant transgene and at least one cytoprotective transgene. In afurther particular embodiment, GTKO animals, tissues and cells areprovided that express at least one immunosuppressant, at least onecomplement inhibitor, at least two anticoagulant transgenes and at leastone anti-cytoprotective transgene. In a particular embodiment, GTKOanimals, tissues and cells are provided that express at least oneimmunosuppressant, at least one complement inhibitor, at least oneanticoagulant transgene and at least one cytoprotective transgene,wherein the expression of the at least one immunosuppressant and the atleast one anticoagulant transgenes is specific to the pancreas. In aparticular embodiment, GTKO animals, tissues and cells are provided thatexpress at least one immunosuppressant, at least one complementinhibitor, at least two anticoagulant transgenes and at least onecytoprotective transgene, wherein the expression of the at least oneimmunosuppressant and the at least two anticoagulant transgenes isspecific to the pancreas. In a specific embodiment, the expression ofthe anti-apoptotic transgene is specific to the pancreas. In oneembodiment, the transgene is specifically expressed in islets, in aparticular embodiment, specific expression in beta cells is provided.

In one embodiment, the transgenic porcine animals described herein areviable. In another embodiment, the animals described herein are fertile.In further embodiments, the animals described herein can stably transmitsome of its genetic modifications to its offspring. In still furtherembodiments, the animals described herein can stably transmit all of itsgenetic modifications to its offspring. In certain embodiments, theanimals can stably transmit all of its genetic modifications to itsoffspring when the animals are bred naturally. In other embodiments, themultiple transgenes exhibit co-segregation to offspring. In particularembodiments, the cells are derived from a pancreas of a viable animal.In particular embodiments, the cells are pancreatic islets. In moreparticular embodiments, the cells are pancreatic beta cells. In certainembodiments, the cells are insulin-producing. In some furtherembodiments, the cells include islet cell clusters. In still furtherembodiments, the cells are islet-like cells.

In a particular embodiment, porcine animal, tissues and cells areprovided with at least the following genetic modifications: lack ofexpression of GT, expression of a complement inhibitor,pancreatic-specific expression of an anticoagulant transgene, andpancreatic-specific expression of an immunosuppressant transgene. In aparticular embodiment, porcine animal, tissues and cells are providedwith at least the following genetic modifications: lack of expression ofGT, expression of a complement inhibitor, pancreatic-specific expressionof two anticoagulant transgenes, and pancreatic-specific expression ofan immunosuppressant transgene. In one embodiment, the transgene isspecifically expressed in an islet cell, in a particular embodiment,specific expression in beta cells is provided.

In another embodiment, porcine animal, tissues and cells are providedwith at least the following genetic modifications: lack of expression ofGT, expression of a complement inhibitor, expression of a cytoprotectivetransgene, pancreatic-specific expression of an anticoagulant transgene,and pancreatic-specific expression of an immunosuppressant transgene. Ina particular embodiment, porcine animal, tissues and cells are providedwith at least the following genetic modifications: lack of expression ofGT, expression of a complement inhibitor, expression of a cytoprotectivetransgene, pancreatic-specific expression of two anticoagulanttransgenes, and pancreatic-specific expression of an immunosuppressanttransgene. In a specific embodiment, the expression of thecytoprotective transgene is also pancreas-specific. In one embodiment,the transgene is specifically expressed in an islet, in a particularembodiment, specific expression in beta cells is provided.

An immunomodulator can be a complement inhibitor or animmunosuppressant. In specific embodiments, the immunomodulator is acomplement inhibitor. The complement inhibitor can be CD46 (or MCP). Inother embodiments, the complement inhibitor is CD55, CD59 or CR1. Incertain embodiments, the transgene is expressed from a ubiquitouspromoter. In certain other embodiments, the transgene is expressed froma promoter active primarily in pancreatic cells. The expression can beat any level, but in specific embodiments, the expression is at highlevels.

An immunomodulator can also be an immunosuppressant. Theimmunosuppressant can be capable of down-regulating a T-cell mediatedresponse. In particular, the immunosuppressant can be CTLA4-Ig ormutants thereof. In other embodiments, the immunosuppressant transgeneis a ligand that interferes with CD28 activity, such as a B7 receptorpeptide or mutant thereof. In certain embodiments, the transgene isexpressed from a promoter active primarily in pancreatic cells. Theexpression can be at any level, but in specific embodiments, theexpression is at high levels.

In other embodiments, the immunomodulator can be selected from the groupthat includes class II transactivators (CIITA) and mutants thereof,PDL1, PDL2, tumor necrosis factor-a.-related apoptosis-inducing ligand(TRAIL), Fas ligand (FasL, CD95L) integrin-associated protein (CD47),HLA-E, HLA-DP, HLA-DQ, or HLA-DR. In certain other embodiments, thetransgene is expressed from a promoter active primarily in pancreaticcells. The expression can be at any level, but in specific embodiments,the expression is at high levels.

In one embodiments, the anticoagulant is selected from the group thatincludes tissue factor pathway inhibitor (TFPI), hirudin,thrombomodulin, endothelial protein C receptor (EPCR), and CD39. In aparticular embodiment, the anticoagulant is TFPI. In another particularembodiment, the anticoagulant is CD39. In certain other embodiments, thetransgene is expressed from a promoter active primarily in pancreaticcells. The expression can be at any level, but in specific embodiments,the expression is at high levels.

The cytoprotective transgene can be an anti-apoptotic, anti-oxidant oranti-inflammatory transgene. In certain embodiments, the cytoprotectivetransgene is selected from the group that includes A20, HO-1, FAT-1, andsoluble TNF-alpha receptor (sTNFRi). In certain other embodiments, thetransgene is expressed from a promoter active primarily in pancreaticcells. The expression can be at any level, but in specific embodiments,the expression is at high levels.

In certain embodiments, the one or more immunosuppressant oranticoagulant transgenes is expressed in pancreatic tissues of GTKOporcine animals which express high levels of CD46. In particularembodiments, porcine animals, tissues and cells are provided derivedfrom GTKO animals that express high levels of CD46 and express TFPI andCTLA4-Ig in pancreatic tissues, and in particular in pancreatic isletcells. In a separate embodiment, porcine animals, tissues and cellsderived from GTKO animals are provided that express high levels of CD46and express CD39 and CTLA4-Ig in pancreatic tissues and in particular inpancreatic islet cells.

In some embodiments, the immunomodulator has the sequence of a humanprotein. In other embodiments, the immunomodulator has the sequence of aporcine protein. In some embodiments, the anticoagulant has the sequenceof a human protein. In other embodiments, the anticoagulant has thesequence of a porcine protein. In some embodiments, the cytoprotectivetransgene has the sequence of a porcine protein. In another embodiment,the cytoprotective transgene has the sequence of a human protein. Inparticular embodiments, the porcine animal, tissue or cell expresses ahuman CD46 transgene. In particular embodiments, the porcine animal,tissue or cell expresses a human CTLA4-Ig transgene. In certainembodiments, the porcine animal, tissue or cell expresses a human TFPI.In certain embodiments, the porcine animal, tissue or cell expresses ahuman CD39. In particular embodiments, the porcine animal, tissue orcell expresses a porcine CD46 transgene. In particular embodiments, theporcine animal, tissue or cell expresses a porcine CTLA4 transgene. Incertain embodiments, the porcine animal, tissue or cell expresses aporcine TFPI. In certain embodiments, the porcine animal, tissue or cellexpresses a porcine CD39.

In a particular embodiment, porcine animal, tissues and cells areprovided with at least the following genetic modifications: lack ofexpression of GT, expression of CD46, pancreatic-specific expression ofTFPI, and pancreatic-specific expression of CTLA4-1g. In anotherparticular embodiment, porcine animal, tissues and cells are providedwith at least the following genetic modifications: lack of expression ofGT, expression of CD46, pancreatic-specific expression of TFPI,pancreatic-specific expression of CD39, and pancreatic-specificexpression of CTLA4-1g. In one embodiment, the transgene is specificallyexpressed in an islet cell, in a particular embodiment, specificexpression in beta cells is provided. In a particular embodiment, theCD46 can be a human CD46. In another particular embodiment, the humanCD46 can be expressed at high levels.

In another particular embodiment, porcine animal, tissues and cells areprovided with at least the following genetic modifications: lack ofexpression of GT, expression of CD46, expression of a cytoprotectivetransgene, pancreatic-specific expression of TFPI, andpancreatic-specific expression of CTLA4-1g. In another particularembodiment, porcine animal, tissues and cells are provided with at leastthe following genetic modifications: lack of expression of GT,expression of CD46, expression of a cytoprotective transgene,pancreatic-specific expression of TFPI, pancreatic-specific expressionof CD39, and pancreatic-specific expression of CTLA4-1g.

In certain embodiments, the transgene is expressed from a promoteractive primarily in pancreatic cells. In certain embodiments thepromoter is a pancreas or islet specific promoter such as the insulinpromoter from a vertebrate animal, including but not limited to fish ormammalian promoters such as tilapia, human, pig, rat, or mouse. Inspecific embodiments, the promoter is a rat-insulin promoter (RIP). Incertain embodiments additional regulatory elements would be incorporatedinto the transgene expression system, including enhancer elements. Theenhancer can be, for example, a pdx-1 enhancer or a chicken actinenhancer, or can be an insulator element for example, a chickenbeta-globin insulator, for enhanced expression of the transgene (Chung JH, Bell A C, Felsenfeld G, Proc Natl Acad Sci USA. 1997 January 21;94(2):575-80).

In certain embodiments, the expression is only in pancreatic tissue andis not in other porcine tissues. In addition, expression can be presentin fetal, neonatal, and mature tissues, each of which can be a source ofdonor islets. In particular embodiments of the invention, the cells, andespecially the pancreatic islet cells, are derived from a transgenicporcine animal and in particular, a transgenic porcine that has grown toa sufficient size to be useful as an adult islet donor. In certainembodiments, the animals survive past weaning age. In specificembodiments, the animals are at least six months old. In certainembodiments, the animal survives to reach breeding age. In certainembodiments, the animal is a porcine animal of at least 300 pounds. In aparticular embodiment, encapsulated islets can be transplanted.

In one embodiment, a method is provided for treatment or prophylaxis ofdiabetes including administering a porcine pancreas tissue,pancreas-derived cells, whole islets, or isolated pancreatic islet cellto a host suffering from diabetes (a diabetic host or diabetic patient),wherein the cell exhibits expresses at least one immunosuppressant andat least one anticoagulant transgene. In another embodiment, islet cellsisolated from porcine animals provided herein are used to treat orreverse diabetes.

In one embodiment, islet cells provided herein can be used to reduce theamount of insulin required by a diabetic host. After the transplant, thepatient may require 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or100% less insulin than that required prior to the transplant. After thetransplant, the host may require about 5% to about 25% less insulin thanthat required prior to the transplant. After the transplant, the hostmay require about 25% to about 50% less insulin than that required priorto the transplant. After the transplant, the host may require about 50%to about 75% less insulin than that required prior to the transplant.After the transplant, the host may require about 75% to about 100% lessinsulin than that required prior to the transplant.

In a particular embodiment, after the transplant, the host may requireless than 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.05, or 0.01 exogenous units ofinsulin per kilogram (kg) per day. In one embodiment, the host after thetransplant requires any number less than about 0.01 to about 0.1exogenous units of insulin per kilogram (kg) per day. In one embodiment,the patient after the transplant requires any number less than about 0.1to about 0.25 exogenous units of insulin per kilogram (kg) per day. Inone embodiment, the patient after the transplant requires any numberless than about 0.25 to about 0.5 exogenous units of insulin perkilogram (kg) per day. In one embodiment, the patient after thetransplant requires any number less than about 0.5 to about 0.6exogenous units of insulin per kilogram (kg) per day.

In one particular embodiment, after the transplant, the patient requiresless than 4 units of insulin/day. In one embodiment, after transplant,the patient requires less than 2 units of insulin/day. In oneembodiment, after the transplant, the patient requires less than 2 unitsof insulin/day. In another embodiment, after transplant, the patientrequires less than 1 unit of insulin per day. In one embodiment, afterthe transplant, the patient requires no exogenous insulin.

In other embodiments, islets provided herein can be used inre-transplant procedures, such procedures may be necessary, for example,in certain embodiments, to maintain sufficient levels of islets tocontrol glycemia long-term.

In certain embodiments of the present invention, methods of treating orpreventing diabetes in primates are provided involving administration ofthe tissues or cells of the present invention to primates in needthereof In one embodiment, the primate is a non-human primate, in onenon-limiting example, a monkey. In another embodiment, the primate is ahuman. In one embodiment, the pancreatic cells are adult cells. Inanother embodiment, the pancreatic cells are fetal or neonatal cells.

In additional embodiments, the animals can also contain geneticmodifications to express an immunomodulator. The immunomodulator can bea complement pathway inhibitor gene and in particular embodiments isselected from CDSS, CD59, CR1 and CD46 (MCP). The complement inhibitorcan be human CD46 (hCD46) wherein expression is through a mini-geneconstruct (See Loveland et al., Xenotransplantation, 11(2):171-183.2004). The immunomodulator can also be an immunosuppressor gene that hasa T-cell modulating effect-such as CTLA4-1g, or a dominant negativeinhibitor of class II MHC (CIITA), or other genes that modulate theexpression of B-cell or T cell mediated immune function. In furtherembodiments, such animals can be further modified to eliminate theexpression of genes which affect immune function.

In additional embodiments, the animals can also contain geneticmodifications to express an anticoagulant. The anticoagulant mayinclude, but is not limited to, TFPI, hirudin, thrombomodulin, EPCR andCD39. In addition, the animals can be genetically modified to inhibitthe expression of a the CMP-Neu5Ac hydroxylase gene (see, for example,U.S. Patent Publication. 2005-0223418), the iGb3 synthase gene (see, forexample, U.S. Patent Publication 2005-0155095), and/or the Forssmansynthase gene (see, for example, U.S. Patent Publication 2006-0068479).In addition, the animals can be genetically modified to reduceexpression of a pro-coagulant. In particular, in one embodiment, theanimals are genetically modified to reduce or eliminate expression of aprocoagulant gene such as the FGL2 (fibrinogen-like protein 2) (see, forexample, Marsden, et al. (2003) J din Invest. 112:58-66; Ghanekar, etal. (2004) J Immunol. 172:5693-701; Mendicino, et al. (2005)Circulation. 112:248-56; Mu, et al. (2007) Physiol Genomics.31(0:53-62).

In embodiments wherein a transgene is expressed, this expression may bevia a ubiquitous or tissue-specific promoter and may include additionalregulatory elements such as enhancers, insulators, matrix attachmentregions (MAR) and the like.

To achieve these additional genetic modifications, in one embodiment,cells isolated from a genetically modified pig can be further modifiedto contain multiple genetic modifications. In some embodiments thesecells can be used as donors to produce pigs with multiple geneticmodifications via nuclear transfer. In other embodiments, geneticallymodified animals can be bred together to achieve multiple geneticmodifications.

Transgenes to Target Acute Humoral Rejection

Xenografting is currently hindered by the severe and well-documentedproblems of rejection. This process can be divided into distinct stages,the first of which occurs within minutes of transplantation and iscalled “hyperacute rejection” (HAR). HAR is defined by the ubiquitouspresence of high titers of pre-formed natural antibodies binding to theforeign tissue. The binding of these natural antibodies to targetepitopes on the donor tissue endothelium is believed to be theinitiating event in HAR. This binding, within minutes of perfusion ofthe donor tissue with the recipient blood, is followed by complementactivation, platelet and fibrin deposition, and ultimately byinterstitial edema and hemorrhage in the donor organ, all of which causerejection of the tissue in the recipient (Strahan et al. (1996)Frontiers in Bioscience 1, e34-41). The primary course of HAR in humansis the natural anti-Gal antibody, which comprises approximately 1% ofantibodies in humans and monkeys.

This initial hyperacute rejection is then reinforced by the delayedvascular response (also known as acute Immoral xenograft rejection(AHXR), acute vascular rejection (AVR) or delayed xenograft rejection(DXR)). The lysis and death of endothelial cells during the hyperacuteresponse is accompanied by edema and the exposure of adventitial cells,which constitutively express tissue factor (TF) on their surface. Tissuefactor is thought to be pivotal in the initiation of the in vivocoagulation cascade, and its exposure to plasma triggers the clottingreactions. Thrombin and TNF-alpha become localized around the damagedtissue and this induces further synthesis and expression of TF byendothelial cells.

The environment around resting endothelial cells does not favorcoagulation. Several natural coagulation inhibitors are associated withthe extracellular proteoglycans of endothelial cells, such as tissuefactor pathway inhibitor, antithrombin III, and thrombomodulin. Therecognition of the foreign tissue by xenoreactive natural antibodies(XNAs), however, causes the loss of these molecules.

Together with the exposure and induction of tissue factor, theanticoagulant environment around endothelial cells thus becomespro-coagulant. The vascularised regions of the xenograft thus becomesites of blood clots, a characteristic of damaged tissue. Blood flow isimpaired and the transplanted organ becomes ischemic. A fuller accountof delayed vascular rejection can be found in Bach et al. (1996) ImmunolToday. 1996 August; 17(8):379-84.

The present invention provides for animals, tissues or cells that may beused in xenotransplantation to produce low to no levels of one or moreof the following: HAR, AHXR/DXR and/or ACXR. In one embodiment, theanimals, tissues or cells may be used in xenotransplantation to producelow to no levels of HAR and AHXR. In another embodiment, the animals,tissues or cells may be used in xenotransplantation to produce low to nolevels of HAR, AHXR and ACXR. As will be discussed in detail in thefollowing sections, embodiments of the present invention include variouscombinations of complement regulator expression, immunosuppressorexpression, anticoagulant expression, and/or partially or fully depletedfunctional αGT expression in donor tissue.

In one embodiment, islet cells isolated from the porcine animalsprovided herein are shown to express one or more transgenes. In furtherembodiments, islet cells from the porcine animals provided herein canelicit a decreased immune response by human lymphocytes (MLR assay) tosaid porcine cells. In another embodiment, islet cells expressingtransgenes are shown to inhibit clotting and thrombosis which occurs inthe xenograft environment.

Alpha 1,3 Galactosyltransferase (αGT)

As noted previously, the primary course of HAR in humans is the naturalanti-galactose alpha 1,3-galactose (Gal) antibody, which comprisesapproximately 1% of IgG antibodies in humans and monkeys. Except for OldWorld monkeys, apes and humans, most mammals carry glycoproteins ontheir cell surfaces that contain the Gal epitope (Galili et al., J.Biol. Chem. 263: 17755-17762, 1988). Humans, apes and old world monkeysdo not express Gal, but rather produce in high quantities a naturallyoccurring anti-Gal antibody that causes an immediate hyperacute reactionupon xenotransplantation into humans of tissues from animals carryingthe Gal epitope (Sandrin et al., Proc Natl Acad Sci US A. 1993 December1; 90(23):11391-5, 1993; review by Sandrin and McKenzie, Immunol Rev.1994 October; 141:169-90).

A variety of strategies have been implemented to eliminate or modulatethe anti-Gal Immoral response caused by xenotransplantation, includingenzymatic removal of the epitope with alpha-galactosidases (Stone etal., Transplantation 63: 640-645, 1997), specific anti-gal antibodyremoval (Ye et al., Transplantation 58: 330-337, 1994), capping of theepitope with other carbohydrate moieties, which failed to eliminate αGTexpression (Tanemura et al., J. Biol. Chem. 27321: 16421-16425, 1998 andKoike et al., Xenotransplantation 4: 147-153, 1997) and the introductionof complement inhibitory proteins (Dalmasso et al., Clin. Exp. Immunol.86:31-35, 1991, Dalmasso et al. Transplantation 52:530-533 (1991)). C.Costa et al. (FASEB J 13, 1762 (1999)) reported that competitiveinhibition of ctGT in transgenic pigs results in only partial reductionin epitope numbers. Similarly, S. Miyagawa et al. (J. Biol. Chem 276,39310 (2000)) reported that attempts to block expression of gal epitopesin N-acetylglucosaminyltransferase III transgenic pigs also resulted inonly partial reduction of gal epitopes numbers and failed tosignificantly extend graft survival in primate recipients.

Single allele knockouts of the ctGT locus in porcine cells and liveanimals have been reported. Denning et al. (Nature Biotechnology 19:559-562, 2001) reported the targeted gene deletion of one allele of thectGT gene in sheep. Harrison et al. (Transgenics Research 11: 143-150,2002) reported the production of heterozygous αGT knock out somaticporcine fetal fibroblasts cells. In 2002, Lai et al. (Science 295:1089-1092, 2002) and Dai et al. (Nature Biotechnology 20: 251255, 2002)reported the production of pigs, in which one allele of the αGT gene wassuccessfully rendered inactive. Ramsoondar et al. (Biol of Reproduc 69,437-445 (2003)) reported the generation of heterozygous αGT knockoutpigs that also express human alpha-1,2-fucosyltransferase (HT), whichexpressed both the HT and αGT epitopes. PCT publication No. WO 031055302to The Curators of the University of Missouri confirms the production ofheterozygous αGT knockout miniature swine for use in xenotransplantationin which expression of functional αGT in the knockout swine is decreasedas compared to the wildtype.

PCT publication No. WO 94/21799 and U.S. Pat. No. 5,821,117 to theAustin Research Institute; PCT publication No. WO 95/20661 to Bresatec;and PCT publication No. WO 95/28412, U.S. Pat. No. 6,153,428, U.S. Pat.No. 6,413,769 and US publication No. 2003/0014770 to BioTransplant, Inc.and The General Hospital Corporation provide a discussion of theproduction of αGT negative porcine cells based on the cDNA of the αGTgene.

A recent, major breakthrough in the field of xenotransplantation was theproduction of the first live pigs lacking any functional expression ofαGT (Phelps et al. Science 299:411-414 (2003); see also PCT publicationNo. WO 04/028243 by Revivicor, Inc. and PCT Publication No. WO 04/016742by Immerge Biotherapeutics, Inc.).

In one embodiment, animals, tissues and cells are provided that lack anyexpression of functional αGT (GTKO) and express at least one additionaltransgene in pancreatic tissues. The additional transgene is typicallyselected from: 1) an immunomodulator including a complement inhibitor(i.e. CD46 (MCP), CDSS, CD59, CR1 and the like) or an immunosuppressor(i.e. CTLA-4, B7 and the like) or 2) an anticoagulant (i.e. TFPI,hirudin, thrombomodulin, EPCR, CD39 and the like). In other embodiments,animals, tissue and cells are provided that lack any expression offunctional αGT and express both at least one immunomodulator and atleast one anticoagulant in pancreatic tissues. In some embodiments, thepancreatic tissue is porcine. In further embodiments, the pancreatictissue comprises pancreatic islet cells, or islets, or islet-cellclusters. In particular embodiments, the cells are pancreatic islets. Inmore particular embodiments, the cells are pancreatic beta cells. Incertain embodiments, the cells are insulin producing. In still furtherembodiments, the cells are islet-like cells. Islet cell clusters caninclude any one or more of alpha, beta, delta, PP or epsilon cells.Generally, alpha cells producing glucagons make up about 15-20% of totalislet cells in native pancreas, bbeta cells producing insulin and amylinmake up between about 65-80% of islet cells in native pancreas, deltacells producing somatostatin make up about 3-10% of total islet cells innative pancreas, PP cells producing pancreatic polypeptide make up about3-5% of total islet cells in native pancreas and epsilon cells producingghrelin make up <1% of total islet cells in native pancreas (see Elayatet al. (1995). J. Anat. 186: 629-37).

Animals, tissues and cells with a reduced level of expression offunctional ctGT that concurrently express at least one of the followingin pancreatic tissues: 1) an immunomodulator including a complementinhibitor (i.e. CD46, CDSS, CD59, CR1 and the like) or animmunosuppressor (i.e. CTLA-4, B7 and the like) or 2) an anticoagulant(i.e. TFPI, hirudin, thrombomodulin, EPCR, CD39 and the like) are alsoincluded in this invention. In some embodiments, animals, tissue andcells are provided that have a reduced level of expression of functionalαGT and express both at least one immunomodulator and at least oneanticoagulant in pancreatic tissues. In some embodiments, the pancreatictissue is porcine. In further embodiments, the pancreatic tissuecomprises pancreatic islet cells. The expression of functional αGT maybe reduced by, for example, by at least about 5%, about 10%, about 20%,about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about90% or about 95%.

The complete or reduced level of expression of functional αGT may beachieved by any means known to one of skill in the art. In one aspect ofthe present invention, porcine animals are provided in which one alleleof the αGT gene is inactivated via a genetic targeting event. In anotheraspect of the present invention, porcine animals are provided in whichboth alleles of the ctGT gene are inactivated via a genetic targetingevent. In one embodiment, the gene can be targeted via homologousrecombination. In other embodiments, the gene can be disrupted, i.e. aportion of the genetic code can be altered, thereby affectingtranscription and/or translation of that segment of the gene. Forexample, disruption of a gene can occur through substitution, deletion(“knock-out”) or insertion (“knock-in”) techniques. Additional genes fora desired protein or regulatory sequence that modulate transcription ofan existing sequence can be inserted.

In embodiments of the present invention, the alleles of the ctGT geneare rendered inactive, such that the resultant ctGT enzyme can no longergenerate Gal on the cell surface. In one embodiment, the ctGT gene canbe transcribed into RNA, but not translated into protein. In anotherembodiment, the ctGT gene can be transcribed in a truncated form. Such atruncated RNA can either not be translated or can be translated into anonfunctional protein. In an alternative embodiment, the αGT gene can beinactivated in such a way that no transcription of the gene occurs. In afurther embodiment, the αGT gene can be transcribed and then translatedinto a nonfunctional protein. In some embodiments, the expression ofactive αGT can be reduced by use of alternative methods, such as thosetargeting transcription or translation of the gene. For example, theexpression can be reduced by use of antisense RNA or siRINA targetingthe native ctGT gene or an mRINA thereof. In other embodiments, sitespecific recombinases are used to target a region of the genome forrecombination. Examples of such systems are the CRE-lox system and theFlp-Frt systems.

Pigs that possess two inactive alleles of the αGT gene are not naturallyoccurring. It was previously discovered that while attempting toknockout the second allele of the ctGT gene through a genetic targetingevent, a point mutation was identified, which prevented the secondallele from producing functional αGT enzyme.

Thus, in another aspect of the present invention, the αGT gene can berendered inactive through at least one point mutation. In oneembodiment, one allele of the αGT gene can be rendered inactive throughat least one point mutation. In another embodiment, both alleles of theαGT gene can be rendered inactive through at least one point mutation.In one embodiment, this point mutation can occur via a genetic targetingevent. In another embodiment, this point mutation can be naturallyoccurring. In a further embodiment, mutations can be induced in the αGTgene via a mutagenic agent.

In one specific embodiment the point mutation can be a T-to-G mutationat the second base of exon 9 of the αGT gene. Pigs carrying a naturallyoccurring point mutation in the αGT gene allow for the production ofaGT-deficient pigs free of antibiotic-resistance genes and thus have thepotential to make a safer product for human use. In other embodiments,at least two, at least three, at least four, at least five, at least tenor at least twenty point mutations can exist to render the αGT geneinactive. In other embodiments, pigs are provided in which both allelesof the αGT gene contain point mutations that prevent any expression offunctional αGT enzyme. In a specific embodiment, pigs are provided thatcontain the T-to-G mutation at the second base of exon 9 in both allelesof the αGT gene.

Another aspect of the present invention provides a porcine animal, inwhich both alleles of the αGT gene are inactivated, whereby one alleleis inactivated by a genetic targeting event and the other allele isinactivated via a mutation. In one embodiment, a porcine animal isprovided, in which both alleles of the αGT gene are inactivated, wherebyone allele is inactivated by a genetic targeting event and the otherallele is inactivated due to presence of a T-to-G point mutation at thesecond base of exon 9. In a specific embodiment, a porcine animal isprovided, in which both alleles of the ctGT gene are inactivated,whereby one allele is inactivated via a targeting construct directed toExon 9 and the other allele is inactivated due to presence of a T-to-Gpoint mutation at the second base of exon 9.

Immunomodulators

Immunomodulators include complement regulators and immunosuppressants.

(i) Complement Regulators

Complement is the collective term for a series of blood proteins and isa major effector mechanism of the immune system. Complement activationand its deposition on target structures can lead to directcomplement-mediated cell lysis or can lead indirectly to cell or tissuedestruction due to the generation of powerful modulators of inflammationand the recruitment and activation of immune effector cells. Complementactivation products that mediate tissue injury are generated at variouspoints in the complement pathway. Inappropriate complement activation onhost tissue plays an important role in the pathology of many autoimmuneand inflammatory diseases, and is also responsible for many diseasestates associated with bioincompatibility, e.g. post-cardiopulmonaryinflammation and transplant rejection. Complement deposition on hostcell membranes is prevented by complement inhibitory proteins expressedat the cell surface.

The complement system comprises a collection of about 30 proteins and isone of the major effector mechanisms of the immune system. Thecomplement cascade is activated principally via either the classical(usually antibody-dependent) or alternative (usuallyantibody-independent) pathways. Activation via either pathway leads tothe generation of C3 convertase, which is the central enzymatic complexof the cascade. C3 convertase cleaves serum C3 into C3a and C3b, thelatter of which binds covalently to the site of activation and leads tothe further generation of C3 convertase (amplification loop). Theactivation product C3b (and also C4b generated only via the classicalpathway) and its breakdown products are important opsonins and areinvolved in promoting cell-mediated lysis of target cells (by phagocytesand NK cells) as well as immune complex transport and solubilization.C3/C4 activation products and their receptors on various cells of theimmune system are also important in modulating the cellular immuneresponse. C3 convertases participate in the formation of C5 convertase,a complex that cleaves C5 to yield C5a and C5b. C5a has powerfulproinflammatory and chemotactic properties and can recruit and activateimmune effector cells. Formation of C5b initiates the terminalcomplement pathway resulting in the sequential assembly of complementproteins C6, C7, C8 and (C9)n to form the membrane attack complex (MACor C5b-9). Formation of MAC in a target cell membrane can result indirect cell lysis, but can also cause cell activation and theexpression/release of various inflammatory modulators.

There are two broad classes of membrane complement inhibitor: inhibitorsof the complement activation pathway (inhibit C3 convertase formation),and inhibitors of the terminal complement pathway (inhibit MACformation). Membrane inhibitors of complement activation includecomplement receptor 1 (CR1), decay-accelerating factor (DAF or CD55) andmembrane cofactor protein (MCP or CD46). They all have a proteinstructure that consists of varying numbers of repeating units of about60-70 amino acids termed short consensus repeats (SCR) that are a commonfeature of C3/C4 binding proteins. Rodent homologues of human complementactivation inhibitors have been identified. The rodent protein Cr1 is awidely distributed inhibitor of complement activation that functionssimilar to both DAF and MCP. Rodents also express DAF and MCP, althoughCr1 appears to be functionally the most important regulator ofcomplement activation in rodents. Although there is no homolog of Cr1found in humans, the study of Cr1 and its use in animal models isclinically relevant.

Control of the terminal complement pathway and MAC formation in hostcell membranes occurs principally through the activity of CD59, a widelydistributed 20 kD glycoprotein attached to plasma membranes by aglucosylphosphatidylinositol (GPI) anchor. CD59 binds to C8 and C9 inthe assembling MAC and prevents membrane insertion.

Host cells are protected from their own complement by membrane-boundcomplement regulatory proteins like DAF, MCP and CD59. When an organ istransplanted into another species, natural antibodies in the recipientbind the endothelium of the donor organ and activate complement, therebyinitiating rapid rejection. It has previously been suggested that, incontrast to human cells, those of the pig are very susceptible to humancomplement, and it was thought that this was because pig cell-surfacecomplement regulatory proteins are ineffective against human complement.When an organ is transplanted into another species, natural antibodiesin the recipient bind the endothelium of the donor organ and activatecomplement, thereby initiating rapid rejection. Several strategies havebeen shown to prevent or delay rejection, including removal of 1 gMnatural antibodies and systemic decomplementation or inhibition ofcomplement using sCR1, heparin or C inhibitor.

An alternative approach to the problem of rejection is to express human,membrane-bound, complement-regulatory molecules in transgenic pigs.Transgenic pigs expressing decay acceleration factor DAF (CD55),membrane co-factor protein MCP (CD46) and membrane inhibitor of reactivelysis, MIRL (CD59) have been generated. (see Klymium et al. Mol ReprodDev (2010)77:209-221). These human inhibitors have been shown to beabundantly expressed on porcine vascular endothelium. Ex vivo perfusionof hearts from control animals with human blood causedcomplement-mediated destruction of the organ within minutes, whereashearts obtained from transgenic animals were refractory to complementand survived for hours.

The rationale for expressing human complement regulatory proteins in pigorgans to “humanize” them as outlined above is based on the assumptionthat endogenous pig regulatory proteins are inefficient at inhibitinghuman complement and thus will contribute little to organ survival inthe context of xenotransplantation. Studies involving pig isletxenotransplantation in non-human primates have shown the importance ofcomplement activation, including deposition of complement components(C3, C5, C9, SC5b-9), and significant binding of 1 gM observed in theislet grafts within 12-24 hours post-transplant. The complementactivation can play an important role in the inflammatory responseassociated with IBMIR which prevents a major portion of infused isletsfrom engrafting (Cantarovich et al., Xenotransplantation 9:25, 2002;Kirchhof et al., Xenotransplantation 11(5), 396, 2004; Tjernberg, etal., Transplantation. 2008 April 27; 85(8): 1193-9). In addition,soluble complement inhibitors can prevent complement-mediated lysis ofislets in vitro (Bennet, et al., Transplantation 69(5):711, 2000).

U.S. Pat. No. 7,462,466 to Morgan et al. describes the isolation andcharacterization of porcine analogues of several of the human complementregulatory proteins (CRP). The studies illustrated that pig organsexpressing human complement regulatory protein molecules were resistantto complement damage not because they expressed human CRP molecules, butbecause they expressed greatly increased amounts of functional CRPmolecules. Morgan et al. found that increased expression of porcine CRPcould be equally effective in protecting the donor organ from complementdamage leading to hyperacute rejection as donor organs expressing humancomplement regulatory proteins.

CD46 has been characterized as a protein with regulatory properties ableto protect the host cell against complement mediated attacks activatedvia both classical and alternative pathways (Barilla-LaBarca, M. L. etal., J. Immunol. 168, 6298-6304 (2002)). hCD46 may offer protectionagainst complement lysis during inflammation and Immoral rejectionmediated by low levels of natural or induced anti-Gal or antinonGalantibodies. As a result, more islets are able to engraft and besubsequently better protected against rejection, thus reducingimmunosuppression needs.

In one embodiment of the present invention, animals, tissues and cellsare provided that express at least one complement regulator and eitherlack any expression of functional αGT or express at least one of thefollowing in pancreatic tissues: 1) an immunosuppressor (i.e. CTLA-4, B7and the like) or 2) an anticoagulant (i.e. TFPI, hirudin,thrombomodulin, EPCR, CD39 and the like).

In other embodiments, animals, tissue and cells are provided thatexpress at least one complement regulator, lack any expression offunctional αGT and express at least one of the following in pancreatictissues: 1) an immunosuppressor (i.e. CTLA4, B7 and the like) or 2) ananticoagulant (i.e. TFPI, hirudin, thrombomodulin, EPCR, CD39 and thelike).

In still further embodiments, animals, tissue and cells are providedthat express at least one complement regulator, lack any expression offunctional aGT, express at least one immunosuppressor (i.e. CTLA-4, B7and the like), and express at least one anticoagulant (i.e. TFPI,hirudin, thrombomodulin, EPCR, CD39 and the like) in pancreatic tissue.In some embodiments, the pancreatic tissue is porcine. In furtherembodiments, the pancreatic tissue comprises pancreatic islet cells.

In some embodiments, the complement regulator may be a complementinhibitor. In further embodiments, the complement inhibitor may be amembrane complement inhibitor. The membrane complement inhibitor may beeither an inhibitor of the complement activation pathway (inhibit C3convertase formation) or an inhibitor of the terminal complement pathway(inhibit MAC formation). Membrane inhibitors of complement activationinclude complement receptor 1 (CR1), decay-accelerating factor (DAF orCD55), membrane cofactor protein (MCP or CD46) and the like. Membraneinhibitors of the terminal complement pathway may include CD59 and thelike. In instances where complement regulators are expressed, two ormore different complement regulators may be expressed.

In some embodiments of the present invention, the complement regulatorsare human complement regulators. In other embodiments, the complementregulators are porcine complement regulators.

In a particular embodiment, the compliment inhibitor (e.g., CD46 or DAF)is expressed in every cell where it would normally be expressed. Inanother embodiment, the compliment inhibitor is expressed ubiquitously.

In one embodiment, the animals, tissues or cells according to thepresent invention, can be modified to transgenically express the one ormore complement regulators. The animals, tissues or cells can bemodified to express a complement regulator peptide, a biologicallyactive fragment or derivative thereof. In one embodiment, the complementregulator peptide is the full length complement regulator. In a furtherembodiment, the complement regulator peptide can contain less than thefull length complement regulator protein.

Any human or porcine complement regulator sequences or biologicallyactive portion or fragment thereof known to one skilled in the art canbe according to the compositions and methods of the present invention.In additional embodiments, any consensus complement regulator peptidecan be used according to the present invention. In another embodiment,nucleic acid and/or peptide sequences at least 80%, 85%, 90% or 95%homologous to the complement regulator peptides and nucleotide sequencesdescribed herein. In further embodiments, any fragment or homologoussequence that exhibits similar activity as complement regulator can beused.

(ii) Immunosuppressants

An “immunosuppressant” transgene is capable of downregulating an immuneresponse. For any type of transplantation procedure, a balance betweenefficacy and toxicity is a key factor for its clinical acceptance. Withrespect to islet transplantation, a further concern is that many of thecurrent immunosuppressive agents in particular glucocortecoids or acalcineurin inhibitor, such as Tarcolimus, damage beta cells or induceperipheral insulin resistance (Zeng et al. Surgery (1993) 113: 98-102).A steroid-free immunosuppressive protocol (“Edmonton protocol”) thatincludes sirolimus, low dose Tarcolimus, and a monoclonal antibody (mAb)against IL-2 receptor has been used in a trial of islet transplantationalone for patients with type-i diabetes (Shapiro, A. M. J. et al,(2000), N. Eng. J. Med., 343: 230-238). The recent success using the“Edmonton protocol” has renewed enthusiasm for the use of islettransplantation to treat diabetes. However, concerns regarding toxicityof the Tacrolimus may limit the application of this therapy in humans.

Biological agents that block key T cell costimulatory signals, inparticular the CD28 pathway, are potential alternatives to protectislets. Examples of agents that block the CD28 pathway include but arenot limited to soluble CTLA4 including mutant CTLA4 molecules.

T-cell activation is involved in the pathogenesis of transplantrejection. Activation of T-cells requires at least two sets of signalingevents. The first is initiated by the specific recognition through theT-cell receptor of an antigenic peptide combined with majorhistocompatibility complex (MHC) molecules on antigen presenting cells(APC5). The second set of signals is antigen nonspecific and isdelivered by T-cell costimulatory receptors interacting with theirligands on APCs. In the absence of costimulation, T-cell activation isimpaired or aborted, which may result in an antigen specificunresponsive state of clonal anergy, or in deletion by apoptotic death.Hence, the blockade of T-cell costimulation may provide an approach forsuppressing unwanted immune responses in an antigen specific mannerwhile preserving normal immune functions. (Dumont, F. J. 2004 Therapy 1,289304).

Of several T cell costimulatory pathways identified to date, the mostprominent is the CD28 pathway. CD28, a cell surface molecule expressedon T-cells, and its counter receptors, the B7.1 (CD80) and B7.2 (CD86)molecules, present on dendritic cells, macrophages, and B-cells, havebeen characterized and identified as attractive targets for interruptingT-cell costimulatory signals. A second T-cell surface moleculehomologous to CD28 is known as cytoxic T-lymphocyte associated protein(CTLA4). CTLA4 is a cell surface signaling molecule, but contrary to theactions of CD28, CTLA4 negatively regulates T cell function. CTLA4 has20-fold higher affinity for the B7 ligands than CD28. The gene for humanCTLA4 was cloned in 1988 and chromosomally mapped in 1990 (Dariavach etal., Eur. J. Immunol. 18:1901-1905 (1988); Lafage-Pochitaloff et al.,Immunogenetics 31:198-201 (1990); U.S. Pat. No. 5,977,318).

The CD28/B7 pathway has become an attractive target for interrupting Tcell costimulatory signals. The design of a CD28/B7 inhibitor hasexploited the endogenous negative regulator of this system, CTLA4. ACTLA4-immunoglobulin (CTLA4-1g) fusion protein has been studiedextensively as a means to inhibit T cell costimulation. A difficultbalance must be reached with any immunosuppressive therapy; one mustprovide enough suppression to overcome the disease or rejection, butexcessive immunosuppression will inhibit the entire immune system. Theimmunosuppressive activity of CTLA4-Ig has been demonstrated inpreclinical studies of animal models of organ transplantation andautoimmune disease. Soluble CTLA4 has recently been tested in humanpatients with kidney failure, psoriasis and rheumatoid arthritis and hasbeen formulated as a drug developed by Bristol-Myers Squibb (Abatacept,soluble CTLA4-1g) that has been approved for the treatment of rheumatoidarthritis. This drug is the first in the new class of selective T cellcostimulation modulators. Bristol-Myers Squibb is also conducting PhaseII clinical trials with Belatacept (LEA29Y) for allograft kidneytransplants. LEA29Y is a mutated form of CTLA41 which has beenengineered to have a higher affinity for the B7 receptors than wild-typeCTLA4, fused to immunoglobulin. Repligen Corporation is also conductingclinical trials with its CTLA4-Ig for idiopathic thrombocytopenicpurpura. U.S. Pat. No. 5,730,403 entitled “Methods for protectingallogeneic islet transplant using soluble CTLA4 mutant molecules”,describes the use of soluble CTLA4-Ig and CTLA4 mutant molecules toprotect allogeneic islet transplants.

Although CTLA-4 from one organism is able to bind to B7 from anotherorganism, the highest avidity is found for allogeneic B7. Thus, whilesoluble CTLA-4 from the donor organism can thus bind to both recipientB7 (on normal cells) and donor B7 (on xenotransplanted cells), itpreferentially binds B7 on the xenograft. Thus in the embodiments of theinvention comprising porcine animals or cells for xenotransplantation,porcine CTLA4 is typical. PCT Publication No. WO 99/5 7266 by ImperialCollege describes a porcine CTLA4 sequence and the administration ofsoluble CTLA4-Ig for xenotransplantation therapy. Vaughn A. et al., JImmunol (2000) 3175-3181, describes binding and function of solubleporcine CTLA4-Ig. Porcine CTLA4-Ig binds porcine (but not human) B7,blocking CD28 on recipient Tcells and rendering these local T cellsanergic without causing global T cell immunosuppression (see Mirenda et.al., Diabetes 54:1048-1055, 2005).

To date, much of the research on CTLA4-Ig as an immunosuppressive agenthas focused on administering soluble forms of CTLA4-Ig to the patient.Transgenic mice engineered to express CTLA4-Ig have been created andsubject to several lines of experimentation. Ronchese et al. examinedimmune system function generally after expression of CTLA4 in mice(Ronchese et al. J Exp Med (1994) 179: 809; Lane et al. J Exp Med.(1994) March 1; 179(3):819). Sutherland et al. (Transplantation. 200069(9):1806-12) described the protective effect of CTLA4-Ig secreted bytransgenic fetal pancreas allografts in mice to test the effects oftransgenically expressed CTLA4-Ig on allogenic islet transplantation.Lui et al. (J Immunol Methods 2003 277: 171-183) reported the productionof transgenic mice that expressed CTLA4-Ig under control of a mammaryspecific promoter to induce expression of soluble CTLA4-Ig in the milkof transgenic animals for use as a bioreactor.

PCT Publication No. WO 01/30966 by Alexion Pharmaceuticals Inc.describes chimeric DNA constructs containing the T cell inhibitor CTLA-4attached to the complement protein CD59, as well as transgenic porcinecells, tissues, and organs containing the same. PCT Publication No.W02007035213 (Revivicor) describes transgenic porcine animals that havebeen genetically modified to express CTLA4-Ig.

Although the development of CTLA4-Ig expressing animals has beensuggested, these animals are severely immunocompromised. Recently, pigsproduced by Revivicor, Inc. expressing CTLA4-Ig ubiquitously using a CAGenhancer/promoter were found to have an immunocompromised phenotype andwere not viable in a typical husbandry environment (see Example 11).

In the current invention, the islet lineage specific enhancer from thePdx-1 gene, known to direct gene expression in both fetal and adultislets (Lomedico et al., 1979), in combination with the promoter fromthe rat Ins2 gene (Gerrish et al., 2004) was utilized to construct avector for driving expression of an immunosuppressant transgene, locallyand specifically, in the islets of the resulting transgenic animals.

Additional immunomodulators, and in particular immunosuppressors can beexpressed in the animals, tissues or cells. For example, genes whichhave been inactivated in mice to produce an immuno compromisedphenotype, can be cloned and disrupted by gene targeting in pigs. Somegenes which have been targeted in mice and may be targeted to produceimmuno compromised pigs include beta 2microglobulin (MHC class Ideficiency, Koller et al., Science, 248:1227-1230), TCR alpha, TCR beta(Mombaerts et al., Nature, 360:225-231), RAG-i and RAG-2 (Mombaerts etal., (1992) Cell 68, 869-877, Shinkai, et al., (1992) Cell 68, 855-867,U.S. Pat. No. 5,859,307).

In one embodiment, the animals or cells according to the presentinvention, can be modified to transgenically express a cytoxicT-lymphocyte associated protein 4-immunoglobin (CTLA4). The animals orcells can be modified to express CTLA4 peptide or a biologically activefragment (e.g., extracellular domain, truncated form of the peptide inwhich at least the transmembrane domain has been removed) or derivativethereof. The peptide may be, e.g., human or porcine. The CTLA4 peptidecan be mutated. Mutated peptides may have higher affinity than wildtypefor porcine and/or human B7 molecules. In one specific embodiment, themutated CTLA4 can be CTLA4 (Glu104, Tyr29). The CTLA4 peptide can bemodified such that it is expressed intracellularly. Other modificationsof the CTLA4 peptide include addition of a endoplasmic reticulumretention signal to the N or C terminus. The endoplasmic reticulumretention signal may be, e.g., the sequence KDEL. The CTLA4 peptide canbe fused to a peptide dimerization domain or an immunoglobulin (Ig)molecule. The CTLA4 fusion peptides can include a linker sequence thatcan join the two peptides. In another embodiment, animals lackingexpression of functional immunoglobulin, produced according to thepresent invention, can be administered a CTLA4 peptide or a variantthereof (pCTLA4-1g, or hCTLA4-Ig (Abatacept/Orencia, or Belatacept) as adrug to suppress their T-cell response. As used herein, CTLA4 is used torefer to any of these variants or those known in the art, e.g.,CTLA4-Ig.

In one embodiment, the CTLA4 peptide is the full length CTLA4. In afurther embodiment, the CTLA4 peptide can contain less than the fulllength CTLA4 protein. In one embodiment, the CTLA4 peptide can containthe extracellular domain of a CTLA-4 peptide. In a particularembodiment, the CTLA4 peptide is the extracellular domain of CTLA4. Instill further embodiments, the present invention provides mutated formsof CTLA4. In one embodiment, the mutated form of CTLA4 can have higheraffinity than wild type for porcine and/or human B7. In one specificembodiment, the mutated CTLA4 can be human CTLA4 (Glu 104, Tyr29).

In one embodiment, the CTLA4 can be a truncated form of CTLA4, in whichat least the transmembrane domain of the protein has been removed. Inanother embodiment, the CTLA4 peptide can be modified such that it isexpressed intracellularly. In one embodiment, a golgi retention signalcan be added to the N or C terminus of the CTLA4 peptide. In oneembodiment, the golgi retention signal can be the sequence KDEL, whichcan be added to the C or N terminal of the CTLA4 peptide. In furtherembodiments, the CTLA4 peptide can be fused to a peptide dimerizationdomain. In one embodiment, the CTLA4 peptide can be fused to animmunoglobulin (Ig). In another embodiment, the CTLA4 fusion peptidescan include a linker sequence that can join the two peptides.

Any human CTLA4 sequences or biologically active portion or fragmentthereof known to one skilled in the art can be according to thecompositions and methods of the present invention. Non-limiting examplesinclude, but are not limited to the following Genbank accession numbersthat describe human CTLA4 sequences: NM005214.2; BC074893.2; BC074842.2;AF414120.1; A17414120; AY402333; AY209009.1; BC070162.1; BC069566.1;L15006.1; AF486806.1; AC010138.6; AJ535718.1; AF225900.1; AF225900;AF411058.1; M37243.1; U90273.1; and/or AF3 16875.1. Further nucleotidesequences encoding CTLA4 peptides can be selected from those including,but not limited to the following Genbank accession numbers from the ESTdatabase: CD639535.1; A1733018.1; BM997840.1; BG536887.1; BG236211.1;BG058720.1; A186009.1; AW207094.1; AA210929.1; A1791416.1; BX113243.1;AW515943.1; BE837454.1; AA210902.1; BF329809.1; A1819438.1; BE837501. 1;BE837537. 1; and/or AA873 138.1.

In additional embodiments, any consensus CTLA4 peptide can be usedaccording to the present invention. In another embodiment, nucleic acidand/or peptide sequences at least 80%, 85%, 90% or 95% homologous to thenative CTLA4 peptides and nucleotide sequences. In further embodiments,any fragment or homologous sequence that exhibits similar activity asCTLA4 can be used.

In other embodiments, the amino acid sequence which exhibits T cellinhibitory activity can be amino acids 38 to 162 of the porcine CTLA4sequence or amino acids 38 to 161 of the human CTLA4 sequence (see, forexample, PCT Publication No. WO 01/30966). In one embodiment, theportion used should have at least about 25% and preferably at leastabout 50% of the activity of the parent molecule.

In other embodiments, the CTLA4 nucleic acids and peptides of thepresent invention can be fused to immunoglobulin genes and molecules orfragments or regions thereof. Reference to the CTLA4 sequences of thepresent invention include those sequences fused to immunoglobulins.

In one embodiment, the Ig can be a human 1g. In another embodiment, theIg can be IgG in particular, IgGi. In another embodiment, the Ig can bethe constant region of IgG In a particular embodiment, the constantregion can be the Cyl chain of IgG 1. In one particular embodiment ofthe present invention, the extracellular domain of porcine CTLA4 can befused to human Cyl 1g. In another particular embodiment, theextracellular domain of human CTLA4 can be fused to IgG 1 or IgG4. In afurther particular embodiment, the extracellular domain of mutated CTLA4(Glu 104, Tyr 29) can be fused to IgGi.

(iii) Other Immunomodulators

Other immunodulators that can be used include class II transactivators(CIITA) and mutants thereof PDL1, PDL2, tumor necrosis factor-O.-relatedapoptosis inducing ligand (TRAIL), Fas ligand (FasL, CD95L)integrin-associated protein (CD47), HLA-E, HLA-DP, HLA-DQ, or HLA-DR.

(a) CIITA: The class II transactivator (CIITA) is a bi- ormultifunctional domain protein that acts as a transcriptional activatorand plays a critical role in the expression of MHC class II genes. Ithas been previously demonstrated that a mutated form of the human CIITAgene, coding for a protein lacking the amino terminal 151 amino acids,acts as a potent dominant-negative suppressor of HLA class II expression(Yun et al., Int Immunol. 1997 October; 9(10):1545-53). Porcine MHCclass II antigens are potent stimulators of direct T-cell recognition byhuman CD4+ T cells and are, therefore, likely to play an important rolein the rejection responses to transgenic pig donors in clinicalxenotransplantation. It was reported that one mutated human CIITAconstruct was effective in pig cells, markedly suppressing IFN[gamma]-induced as well as constitutive porcine MHC class II expression.Moreover, stably transfected porcine vascular endothelial cell linescarrying mutated human CITTA constructs failed to stimulate directT-cell xenorecognition by purified human CD4+ T cells (Yun et al.,Transplantation. 2000 March 15; 69(5):940-4). Organs, tissues and cellsfrom CIITA-DN transgenic animals could induce a much reduced T-cellrejection responses in human recipients. In combination with othertransgenes, transgenic expression of a mutated CIITA might enablelong-term xenograft survival with clinically acceptable levels ofimmunosuppression.

(b) PDL1, PDL2: Typical costimulatory molecules for T-cell activationare CD80/86 or CD40. In addition to these positive costimulatorypathways over the past several years, new costimulatory pathways thatmediate negative signals and are important for the regulation of T-cellactivation have been found. One of these newer pathways is the pathwayconsisting of Programmed death 1 (PD-1) receptor and its ligands, PD-Liand PD-L2. The PD-i receptor is not expressed in resting cells but isupregulated after T and B cell activation. PD-i contains a cytoplasmaticimmunoreceptor tyrosine-based switch motif and binding of PD-Li or PD-L2to PD-i leads to inhibitory signals in T cells. Recent data suggest thatPDi/PDLigand pathways may play a role in the control of T-cell subsetsexhibiting regulatory activity. In mice, PD-i signals have been shown tobe required for the suppressive activity of regulatory T cells (Treg)and the generation of adaptive Treg. These observations suggest thatPD-i/PDLig and interactions do not only inhibit T-cell responses but mayalso provoke immunoregulation. Several lines of evidence demonstratethat PD-i/PDLigand pathways can control engraftment and rejection ofallografts implying that these molecules are interesting targets forimmunomodulation after organ transplantation. Indeed, prolongation ofallograft survival could be obtained by PDLiIg gene transfer to donorhearts in a rat transplantation model. Moreover, enhancing PD-isignaling by injection of PD-Lug has also been reported to protectgrafts from rejection in mice. Recent data also show that overexpressionof PD-LuG on islet grafts in mice can partially prolong islet graftsurvival. Transgenic expression of human PD-Li or PD-L2 in pig cells andtissues should reduce early human anti-pig T-cell responses initiatedvia the direct route of sensitization (Plege et al., Transplantation.2009 April 15; 87(7):975-82). By the induction of Treg it might also bepossible to control T cells sensitized to the xenograft through theindirect route that is required to achieve long-lasting tolerance.

(c) TRAIL/Fas L:

Expression of apoptosis inducing ligands, such as Fas ligand (FasL,CD95L) or tumor necrosis factor-α-related apoptosis-inducing ligand(TRAIL, Apo-2L) may eliminate T cells attacking a xenograft. TRAIL is atype II membrane protein with an extracellular domain homologous to thatof other tumor necrosis factor family members showing the highest aminoacid identity to FasL (28%). TRAIL exerts its apoptosis-inducing actionpreferentially on tumor cells. In normal cells, binding of TRAILreceptors does not lead to cell death. Recent studies have shown thatthe cytotoxic effects of immune cells, including T cells, natural killercells, macrophages, and dendritic cells, are mediated at least partly byTRAIL. Expression of human TRAIL in transgenic pigs may provide areasonable strategy for protecting pig tissues against cell-mediatedrejection after xenotransplantation to primates. Stable expression ofhuman TRAIL has been achieved in transgenic pigs and TRAIL expressed hasbeen shown to be biologically functional in vitro (Klose et al.,Transplantation. 2005 July 27; 80(2):222-30).

(d) CD47: CD47, known as integrin-associated protein, is a ubiquitouslyexpressed 50-kDa cell surface glycoprotein that serves as a ligand forsignal regulatory protein (SIRP)α (also known as CD172a, SHPS-1), animmune inhibitory receptor on macrophages. CD47 and SIRPct constitute acell-cell communication system (the CD47-SIRPα system) that playsimportant roles in a variety of cellular processes including cellmigration, adhesion of B cells, and T cell activation. In addition, theCD47-SIRPa system is implicated in negative regulation of phagocytosisby macrophages. CD47 on the surface of several cell types (i.e.,erythrocytes, platelets, or leukocytes) can protect against phagocytosisby macrophages by binding to the inhibitory macrophage receptor SIRPα.The role of CD47-SIRPα interactions in the recognition of self andinhibition of phagocytosis has been illustrated by the observation thatprimary, wild-type mouse macrophages rapidly phagocytose unopsonizedRBCs obtained from CD47-deficient mice but not those from wild-typemice. It has also been reported that through its SIRPa receptors, CD47inhibits both Fcy and complement receptor-mediated phagocytosis. It hasbeen demonstrated that porcine CD47 does not induce SIRPa tyrosinephosphorylation in human macrophage-like cell line, and soluble humanCD47-Fc fusion protein inhibits the phagocytic activity of humanmacrophages toward porcine cells. It was also indicated thatmanipulation of porcine cells for expression of human CD47 radicallyreduces the susceptibility of the cells to phagocytosis by humanmacrophages (Ide et al., Proc Natl Acad Sci USA. 2007 March 20;104(12):5062-6). Expression of human CD47 on porcine cells could provideinhibitory signaling to SIRPα on human macrophages, providing anapproach to preventing macrophage-mediated xeno graft rejection.

(e) NK Cell Response. HLA-E/Beta 2 Microglobulin and HLA-DP, HLA-DO,HLA-DR:

Human natural killer (NK) cells represent a potential hurdle tosuccessful pigto-human xenotransplantation because they infiltrate pigorgans perfused with human blood ex vivo and lyse porcine cells in vitroboth directly and, in the presence of human serum, by antibody-dependentcell-mediated cytotoxicity. NK cell autoreactivity is prevented by theexpression of major histocompatibility complex (MHC) class I ligands ofinhibitory NK receptors on normal autologous cells. The inhibitoryreceptor CD94/NKG2A that is expressed on a majority of activated humanNKcells binds specifically to human leukocyte antigen(HLA)-E. Thenonclassical human MHC molecule HLA-E is a potent inhibitory ligand forCD94/NKG2A-bearing NK cells and, unlike classical MHC molecules, doesnot induce allogeneic T-cell responses. HLA-E is assembled in theendoplasmic reticulum and transported to the cell surface as a stabletrimeric complex consisting of the HLAE heavy chain, β2-microglobulin (β2m), and a peptide derived from the leader sequence of some MHC class Imolecules. The expression of HLA-E has been shown to provide partialprotection against xenogeneic human NK cell cytotoxicity (Weiss et al.,Transplantation. 2009 January 15; 87(1):35-43). Transgenic expression ofHLA-E on pig organs has the potential to substantially alleviate humanNK cell-mediated rejection of porcine xenografts without the risk ofallogeneic responses. In addition, transgenic pigs carrying other HLAgenes have been successfully generated with the goal of “humanizing”porcine organs, tissues, and cells (Huang et al., Proteomics. 2006November; 6(21):5815-25, see also U.S. Pat. No. 6,639,122).

Anti-Coagulants

The islet-blood reaction is characterized by accelerated clotting andplatelet consumption, resulting in loss of 80-90% of the islet mass inthe first 48 hours, and has been shown to be associated with activationof the complement lysis system, and upregulation of tissue factor on theislets (Johansson et al. Diabetes, 2005, 54:1755; Moberg et al, Lancet,2002, 360:1999-2000; Berman et al., Transplantation 2007, 84:308-313).Previously, these anticoagulant transgenes have been introduced intoanimals with the goal of expressing them in the porcine endothelium fororgan xenotransplantation. In the current invention, the islet lineagespecific enhancer from the Pdx-1 gene, known to direct gene expressionin both fetal and adult islets (Lomedico P et al., Cell, 1979, 18:545),in combination with the promoter from the rat Ins2 gene (Gerrish K etal., Mol. Endocrinol., 2004, 18(3): 533) was utilized to construct avector for driving expression of an anticoagulant, locally andspecifically, in the islets of the resulting transgenic animals.

Tissue factor pathway inhibitor (TFPI) is a single-chain polypeptidewhich can reversibly inhibit Factor Xa (Xa) and Thrombin (Factor IIa)and thus inhibits TF dependent coagulation. For a review of TFPI, pleasesee Crawley and Lane (Arterioscler Thromb Vase Biol. 2008,28(2):233-42). Dorling and colleagues generated transgenic miceexpressing a fusion protein consisting of the three Kunitz domains ofhuman TFPI linked to the transmembrane/cytoplasmic domains of human CD4,with a P-selectin tail for targeting to Weibel-Palade intracellularstorage granules (Chen D, et al. Am J Transplant 2004; 4: 1958-1963.).The resulting activation-dependent display of TFPI on the endotheliumwas sufficient to completely inhibit thrombosis-mediated acute Immoralrejection of mouse cardiac xenografts by cyclosporine-treated rats.There was also a suggestion that effective regulation of coagulation mayprevent chronic rejection. Similar results were obtained with transgenicmouse hearts expressing a hirudin/CD4/P-selectin fusion protein,indicating that inhibition of thrombin generation or activity was thekey to protection in this model.

Hirudin is a naturally occurring peptide in the salivary glands ofmedicinal leeches (such as Hirudo medicinalis) and is a potent inhibitorof thrombin. Dorling and coworkers (Chen et al., J Transplant. 2004December; 4(12):1958-63) also generated transgenic mice expressingmembrane-tethered hirudin fusion proteins, and transplanted their heartsinto rats (mouse-rat Xeno-Tx). In contrast to control nontransgenicmouse hearts, which were all rejected within 3 days, 100% of the organsfrom both strains of transgenic mice were completely resistant toImmoral rejection and survived for more than 100 days whenT-cell-mediated rejection was inhibited by administration of ciclosporinA. Riesbeck et al., (Circulation. 1998 December 15; 98(24):2744-52) alsoexplored the expression of hirudin fusion proteins in mammalian cells asa strategy for prevention of intravascular thrombosis. Expression incells reduced local thrombin levels and inhibited fibrin formation.Therefore, hirudin is another anticoagulant transgene of interest forpreventing the thrombotic effects present in xenotransplantation.

Thrombomodulin (TM) functions as a cofactor in the thrombin-inducedactivation of protein C in the anticoagulant pathway by forming a 1:1stoichiometric complex with thrombin. Endothelial cell protein Creceptor (EPCR) is an Nglycosylated type I membrane protein thatenhances the activation of protein C. The role of these proteins in theprotein C anticoagulant system is reviewed by Van de Wouwer et al.,Arterioscler Thromb Vase Biol. 2004 August; 24(8):1374-83. Expression ofthese and other anticoagulant transgenes has been explored by variousgroups to potentially address the coagulation barriers toxenotransplantation (reviewed by Cowan and D'Apice, Cur Opin OrganTransplant. 2008 April; 13(2):178-83). Esmon and coworkers (Li et al., JThromb Haemost. 2005 July; 3(7):1351-9 over-expressed EPCR on theendothelium of transgenic mice and showed that such expression protectedthe mice from thrombotic challenge. lino et al., (J Thromb Haemost. 2004May; 2(5):833-4), suggested ex-vivo over expression of TM in donorislets via gene therapy as a means to prevent thrombotic complicationsin islet transplantation.

CD39 is a major vascular nucleoside triphosphate diphosphohydrolase(NTPDa5e), and converts ATP, and ADP to AMP and ultimately adenosine.Extracellular adenosine plays an important role in thrombosis andinflammation, and thus has been studied for its beneficial role intransplantation (reviewed by Robson et al. Semin Thromb Hemost. 2005April; 31(2):217-33). Recent studies have shown that CD39 has a majoreffect in reducing the inflammatory response (Beldi et al., FrontBiosci, 2008, 13:2588-2603). Transgenic mice expressing hCD39 exhibitedimpaired platelet aggregation, prolonged bleeding times, and resistanceto systemic thromboembolism in a heart transplant model (Dwyer et al., JClin Invest. 2004 May; 113(10): 1440-6). They were also shown to expressCD3 9 on pancreatic islets and when incubated with human blood, theseislets significantly delayed clotting time compared to wild type islets(Dwyer et al., Transplantation. 2006 August 15; 82(3):42832).Preliminary efforts at expressing hCD39 at high levels from aconstitutive promoter system in transgenic pigs, showed high post-natallethality (Revivicor, Inc., unpublished data). Thus there is a need toexpress anticoagulant transgenes in pigs in a manner that does notcompromise the animal's well being, yet still provides adequate levelsof expression for utility in clinical xenotransplantation.

Cytoprotective Transgenes

The present invention includes cytoprotective transgenes(“cytoprotectants’). Cytoprotective transgenes are considered to includeanti-apoptotics, anti-oxidants and anti-inflammatories. Examplesinclude:

(a) A20:

A20 provides anti-inflammatory and anti-apoptotic activity. Vascularizedtransplanted organs may be protected against endothelial cell activationand cellular damage by anti-inflammatory, anticoagulant and/oranti-apoptotic molecules. Among genes with great potential formodulation of acute vascular rejection (AVR) is the human A20 gene(hA20) that was first identified as a tumor necrosis factor (TNF)-αinducible factor in human umbilical vein endothelial cells. Human A20has a double cytoprotective function by protecting endothelial cellsfrom TNF-mediated apoptosis and inflammation, via blockade of severalcaspases, and the transcription factor nuclear factor-κB, respectively.Viable A20 transgenic piglets have been produced and in these animalsexpression of hA20 was restricted to skeletal muscle, heart and PAECswhich were protected against TNF mediated apoptosis by hA20 expressionand at least partly against CD95(Fas)L-mediated cell death. In addition,cardiomyocytes from hA20-transgenic-cloned pigs were partially protectedagainst cardiac insults (Oropeza et al., Xenotransplantation. 2009November; 16(6):522-34).

(b) HO-1:

HO provides anti-inflammatory, anti-apoptotic, and anti-oxidantactivity. Herne oxygenases (HOs), rate-limiting enzymes in hemecatabolism, also named HSP32, belong to members of heat shock proteins,wherein the heme ring is cleaved into ferrous iron, carbon monoxide (CO)and biliverdin that is then converted to bilirubin by biliverdinreductase. Three isoforms of HOs, including HO-1, HO-2 and HO-3, havebeen cloned. The expression of HO-1 is highly inducible, whereas HO-2and HO-3 are constitutively expressed (Maines M D et al., Annual Reviewof Pharmacology & Toxicology 1997; 37:517-554, and Choi A M et al.,American Journal of Respiratory Cell & Molecular Biology 1996; 15:9-19).An analysis of HO-1−/− mice suggests that the gene encoding HO-1regulates iron homeostasis and acts as a cytoprotective gene havingpotent antioxidant, anti-inflammatory and antiapoptotic effects (Poss KD et al., Proceedings of the National Academy of Sciences of the UnitedStates of America 1997; 94:10925-10930, Poss K D et al., Proceedings ofthe National Academy of Sciences of the United States of America 1997;94:10919-10924, and Soares M P et al., Nature Medicine 1998;4:1073-1077). Similar findings were recently described in a case reportof HO-1 deficiency in humans (Yachie A et al., Journal of ClinicalInvestigation 1999; 103:129-135). The molecular mechanisms responsiblefor the cytoprotective effects of HO-1, including anti-inflammation,anti-oxidation and anti-apoptosis, are mediated by its' reactionproducts. HO-1 expression can be modulated in vitro and in vivo byprotoporphyrins with different metals. Cobalt protoporphyrins (CoPP) andiron protoporphyrins (FePP) can up-regulate the expression of HO-1. Incontrast, tin protoporphyrins (SnPP) and zinc protoporphyrins (ZnPP)inhibit the activity of HO-1 at the protein level. Recently, it has beenproved that the expression of HO-1 suppresses the rejection ofmouse-to-rat cardiac transplants (Sato K et al., J. Immunol. 2001;166:4185-4194), protects islet cells from apoptosis, and improves the invivo function of islet cells after transplantation (Pileggi A et al.,Diabetes 2001; 50: 1983-1991). It has also been proved thatadministration of HO-1 by gene transfer provides protection againsthyperoxia-induced lung injury (Otterbein L E et al., J Clin Invest 1999;103: 1047-1054), upregulation of HO-1 protects genetically fat Zuckerrat livers from ischemia/reperfusion injury (Amersi F et al., J ClinInvest 1999; 104: 1631-1639), and ablation or expression of HO-1 genemodulates cisplatin-induced renal tubular apoptosis (Shiraishi F et al.,Am J Physiol Renal Physiol 2000; 278:17726-17736). In transgenic animalmodels, it was shown that over-expression of HO-1 prevents the pulmonaryinflammatory and vascular responses to hypoxia (Minamino T et al., Proc.Natl. Acad. Sci. USA 2001; 98:8798-8803) and protects heart againstischemia and reperfusion injury (Yet S F, et al., Cir Res 2001;89:168-173). Pigs carrying a HO-1 transgene have been produced howeverclinical effects related to their use in xenotransplantation were notreported (U.S. Pat. No. 5,737,8569).

(c) FAT-1:

FAT-1 provides anti-inflammatory activity. Polyunsaturated fatty acids(PUFAs) play a role in inhibiting (n-3 class) inflammation. Mammaliancells are devoid of desaturase that converts n-6 to n-3 PUFAs.Consequently, essential n-3 fatty acids must be supplied with the diet.Unlike mammals, however, the free-living nematode Caenorhabditis elegansexpresses a n-3 fatty acid desaturase that introduces a double bond inton-6-fatty acids at the n-3 position of the hydrocarbon chains to formn-3 PUFAs. Transgenic mice have been generated that express the C.elegans fat-i gene and, consequently, are able to efficiently convertdietary PUFAs of the 6 series to PUFAs of 3-series, such as EPA (20:5n-3) and DHA (22-6 n-3). (Kang et al., Nature. 2004 February 5;427(6974):504). Another group produced a transgenic mouse model whereinthe codons of fat-i cDNA were further optimized for efficienttranslation in mammalian systems; endogenous production of n-3 PUFAs wasachieved through overexpressing a C. elegans n-3 fatty acid desaturasegene, mfat-1. This group showed that cellular increase of n-3 PUFAs andreduction of n-6 PUFAs through transgenic expression of mfat-1 enhancedglucose-, amino acid-, and GLP-1-stimulated insulin secretion inisolated pancreatic islets of the mice, and rendered the islets stronglyresistant to cytokine-induced cell death (Wei et al., Diabetes. 2010February; 59(2):471-8).

(d) Soluble TNF-Alpha Receptor (sTNFR1):

Tumor necrosis factor (TNF, cachexin or cachectin and formally known astumor necrosis factor-alpha) is a cytokine involved in systemicinflammation and is a member of a group of cytokines that stimulate theacute phase reaction. The primary role of TNF is in the regulation ofimmune cells. TNF is able to induce apoptotic cell death, to induceinflammation. Soluble TNF-alpha receptor 1 (sTNFR1) is an extracellulardomain of TNFR1 and an antagonist to TNF-alpha (Su et al., 1998.Arthritis Rheum. 41, 139-149). Transgenic expression of sTNFR1 inxenografts may have beneficial anti-inflammatory effects.

Other cytoprotectives with relevant anti-oxidant properties include,without limitation, SOD and Catalyse. Oxygen is the essential moleculefor all aerobic organisms, and plays predominant role in ATP generation,namely, oxidative phosphorylation. During this process, reactive oxygenspecies (ROS) including superoxide anion (0(2)(−)) and hydrogen peroxide(H(2)0(2)) are produced as byproducts. In man, an antioxidant defensesystem balances the generation of ROS. Superoxide dismutase (SOD) andcatalase are two enzymes with anti-oxidant properties. SOD catalyses thedismutation of superoxide radicals to hydrogen peroxide, the latterbeing converted to water by catalase and glutathione peroxidase.Cellular damage resulting from generation of ROS can occur in atransplant setting. Because of reduced antioxidant defenses, pancreaticbeta-cells are especially vulnerable to free radical and inflammatorydamage. Commonly used antirejection drugs are excellent at inhibitingthe adaptive immune response; however, most are harmful to islets and donot protect well from reactive oxygen species and inflammation resultingfrom islet isolation and ischemia-reperfusion injury. Therefore there isan interest in treating islets ex-vivo with anti-oxidants, or expressinganti-oxidant genes via gene therapy or transgenic expression in donortissues. Ex vivo gene transfer of EC-SOD and catalase wereanti-inflammatory in a rat model of antigen induced arthritis (Dai etal., Gene Ther. 2003 April; 10(7):550-8). In addition, delivery ofEC-SOD and/or catalase genes through the portal vein markedly attenuatedhepatic hR injury in a mouse model (He et al., Liver Transpl. 2006December; 12(12):1869-79). In a recent mouse study, pancreatic isletstreated with catalytic antioxidant before syngeneic, suboptimalsyngeneic, or xenogeneic transplant exhibited superior function comparedwith untreated controls. In this same study, diabetic murine recipientsof catalytic antioxidant-treated allogeneic islets exhibited improvedglycemic control post-transplant and demonstrated a delay in allograftrejection (Sklavos et al., Diabetes. 2010 July; 59(7):1731-8. Epub 2010April 22). In another mouse study, islet grafts overexpressing MnSODfunctioned approximately 50% longer than control grafts (Bertera et al.,Diabetes. 2003 February; 52(2):387-93).

Moreover, certain anti-coagulants also provide anti-inflammatoryactivity including thrombomodulin, EPCR and CD39.

Production of Genetically Modified Animals

Genetically modified animals can be produced by any method known to oneof skill in the art including, but not limited to, selective breeding,nuclear transfer, introduction of DNA into oocytes, sperm, zygotes, orblastomeres, or via the use of embryonic stem cells.

In some embodiments, genetic modifications may be identified in animalsthat are then bred together to form a herd of animals with a desired setof genetic modifications (or a single genetic modification). Theseprogeny may be further bred to produce different or the same set ofgenetic modifications (or single genetic modification) in their progeny.This cycle of breeding for animals with desired genetic modification(s)may continue for as long as one desires. “Herd” in this context maycomprise multiple generations of animals produced over time with thesame or different genetic modification(s). “Herd” may also refer to asingle generation of animals with the same or different geneticmodification(s).

Cells useful for genetic modification (via, for example, but not limitedto, homologous recombination) include, by way of example, epithelialcells, neural cells, epidermal cells, keratinocytes, hematopoieticcells, melanocytes, chondrocytes, lymphocytes (B and T lymphocytes),erythrocytes, macrophages, monocytes, mononuclear cells, fibroblasts,cardiac muscle cells, and other muscle cells, etc. Moreover, the cellsused for producing the genetically modified animal (via, for example,but not limited to, nuclear transfer) can be obtained from differentorgans, e.g., skin, lung, pancreas, liver, stomach, intestine, heart,reproductive organs, bladder, kidney, urethra and other urinary organs,etc. Cells can be obtained from any cell or organ of the body, includingall somatic or germ cells.

Additionally, animal cells that can be genetically modified can beobtained from a variety of different organs and tissues such as, but notlimited to, skin, mesenchyme, lung, pancreas, heart, intestine, stomach,bladder, blood vessels, kidney, urethra, reproductive organs, and adisaggregated preparation of a whole or part of an embryo, fetus, oradult animal. In one embodiment of the invention, cells can be selectedfrom the group consisting of, but not limited to, epithelial cells,fibroblast cells, neural cells, keratinocytes, hematopoietic cells,melanocytes, chondrocytes, lymphocytes (B and T), macrophages,monocytes, mononuclear cells, cardiac muscle cells, other muscle cells,granulosa cells, cumulus cells, epidermal cells, endothelial cells,Islets of Langerhans cells, blood cells, blood precursor cells, bonecells, bone precursor cells, neuronal stem cells, primordial stem cells,adult stem cells, mesenchymal stem cells, hepatocytes, keratinocytes,umbilical vein endothelial cells, aortic endothelial cells,microvascular endothelial cells, fibroblasts, liver stellate cells,aortic smooth muscle cells, cardiac myocytes, neurons, Kupffer cells,smooth muscle cells, Schwann cells, and epithelial cells, erythrocytes,platelets, neutrophils, lymphocytes, monocytes, eosinophils, basophils,adipocytes, chondrocytes, pancreatic islet cells, thyroid cells,parathyroid cells, parotid cells, tumor cells, glial cells, astrocytes,red blood cells, white blood cells, macrophages, epithelial cells,somatic cells, pituitary cells, adrenal cells, hair cells, bladdercells, kidney cells, retinal cells, rod cells, cone cells, heart cells,pacemaker cells, spleen cells, antigen presenting cells, memory cells, Tcells, B-cells, plasma cells, muscle cells, ovarian cells, uterinecells, prostate cells, vaginal epithelial cells, sperm cells, testicularcells, germ cells, egg cells, leydig cells, peritubular cells, sertolicells, lutein cells, cervical cells, endometrial cells, mammary cells,follicle cells, mucous cells, ciliated cells, nonkeratinized epithelialcells, keratinized epithelial cells, lung cells, goblet cells, columnarepithelial cells, squamous epithelial cells, osteocytes, osteoblasts,and osteoclasts. In one alternative embodiment, embryonic stem cells canbe used. An embryonic stem cell line can be employed or embryonic stemcells can be obtained freshly from a host, such as a porcine animal. Thecells can be grown on an appropriate fibroblast-feeder layer or grown inthe presence of leukemia inhibiting factor (LIF).

Embryonic stem cells are a preferred germ cell type, an embryonic stemcell line can be employed or embryonic stem cells can be obtainedfreshly from a host, such as a porcine animal. The cells can be grown onan appropriate fibroblast-feeder layer or grown in the presence ofleukemia inhibiting factor (LIF).

Cells of particular interest include, among other lineages, stem cells,e.g. hematopoietic stem cells, embryonic stem cells, mesenchymal stemcells, etc., the islets of Langerhans, adrenal medulla cells which cansecrete dopamine, osteoblasts, osteoclasts, epithelial cells,endothelial cells, leukocytes, e.g. B- and T-lymphocytes, myelomonocyticcells, etc., neurons, glial cells, ganglion cells, retinal cells, livercells, e.g. hepatocytes, bone marrow cells, keratinocytes, hair folliclecells, and myoblast (muscle) cells.

In a particular embodiment, the cells can be fibroblasts orfibroblast-like cells having a morphology or a phenotype that is notdistinguishable from fibroblasts, or a lifespan before senescence of atleast 10 or at least 12 or at least 14 or at least 18 or at least 20days, or a lifespan sufficient to allow homologous recombination andnuclear transfer of a non-senescent nucleus; in one specific embodiment,the cells can be fetal fibroblasts. Fibroblast cells are a suitablesomatic cell type because they can be obtained from developing fetusesand adult animals in large quantities. These cells can be easilypropagated in vitro with a rapid doubling time and can be clonallypropagated for use in gene targeting procedures. The cells to be usedcan be from a fetal animal, or can be neonatal or from an adult animalin origin. The cells can be mature or immature and either differentiatedor non-differentiated.

Homologous Recombination

Homologous recombination permits site-specific modifications inendogenous genes and thus novel alterations can be engineered into thegenome. A primary step in homologous recombination is DNA strandexchange, which involves a pairing of a DNA duplex with at least one DNAstrand containing a complementary sequence to form an intermediaterecombination structure containing heteroduplex DNA (see, for exampleRadding, C. M. (1982) Ann. Rev. Genet. 16: 405; U.S. Pat. No.4,888,274). The heteroduplex DNA can take several forms, including athree DNA strand containing triplex form wherein a single complementarystrand invades the DNA duplex (Hsieh et al. (1990) Genes and Development4: 1951; Rao et al., (1991) PNAS 88:2984)) and, when two complementaryDNA strands pair with a DNA duplex, a classical Holliday recombinationjoint or chi structure (Holliday, R. (1964) Genet. Res. 5: 282) canform, or a double-D loop (“Diagnostic Applications of Double-D LoopFormation” U.S. Ser. No. 07/755,462, filed Sep. 4, 1991). Once formed, aheteroduplex structure can be resolved by strand breakage and exchange,so that all or a portion of an invading DNA strand is spliced into arecipient DNA duplex, adding or replacing a segment of the recipient DNAduplex. Alternatively, a heteroduplex structure can result in geneconversion, wherein a sequence of an invading strand is transferred to arecipient DNA duplex by repair of mismatched bases using the invadingstrand as a template (Genes, 3rd Ed. (1987) Lewin, B., John Wiley, NewYork, N.Y.; Lopez et al. (1987) Nucleic Acids Res. 15: 5643). Whether bythe mechanism of breakage and rejoining or by the mechanism(s) of geneconversion, formation of heteroduplex DNA at homologously paired jointscan serve to transfer genetic sequence information from one DNA moleculeto another.

The ability of homologous recombination (gene conversion and classicalstrand breakage/rejoining) to transfer genetic sequence informationbetween DNA molecules renders targeted homologous recombination apowerful method in genetic engineering and gene manipulation.

In homologous recombination, the incoming DNA interacts with andintegrates into a site in the genome that contains a substantiallyhomologous DNA sequence. In non-homologous (“random” or “illicit”)integration, the incoming DNA is not found at a homologous sequence inthe genome but integrates elsewhere, at one of a large number ofpotential locations. In general, studies with higher eukaryotic cellshave revealed that the frequency of homologous recombination is far lessthan the frequency of random integration. The ratio of these frequencieshas direct implications for “gene targeting” which depends onintegration via homologous recombination (i.e. recombination between theexogenous “targeting DNA” and the corresponding “target DNA” in thegenome). The present invention can use homologous recombination toinactivate a gene or insert and upregulate or activate a gene in cells,such as the cells described above. The DNA can comprise at least aportion of the gene(s) at the particular locus with introduction of analteration into at least one, optionally both copies, of the nativegene(s), so as to prevent expression of functional gene product. Thealteration can be an insertion, deletion, replacement, mutation orcombination thereof. When the alteration is introduced into only onecopy of the gene being inactivated, the cells having a single unmutatedcopy of the target gene are amplified and can be subjected to a secondtargeting step, where the alteration can be the same or different fromthe first alteration, usually different, and where a deletion, orreplacement is involved, can be overlapping at least a portion of thealteration originally introduced. In this second targeting step, atargeting vector with the same arms of homology, but containing adifferent mammalian selectable markers can be used. The resultingtransformants are screened for the absence of a functional targetantigen and the DNA of the cell can be further screened to ensure theabsence of a wild-type target gene. Alternatively, homozygosity as to aphenotype can be achieved by breeding hosts heterozygous for themutation.

A number of papers describe the use of homologous recombination inmammalian cells. Illustrative of these papers are Kucherlapati et al.(1984) Proc. Natl. Acad. Sci. USA 81:3153-3157; Kucherlapati et al.(1985) Mol. Cell. Bio. 5:714720; Smithies et al. (1985) Nature317:230-234; Wake et al. (1985) Mol. Cell. Bio. 8:2080-2089; Ayares etal. (1985) Genetics 111:375-388; Ayares et al. (1986) Mol. Cell. Bio.7:1656-1662; Song et al. (1987) Proc. Natl. Acad. Sci. USA 84:6820-6824;Thomas et al. (1986) Cell 44:419-428; Thomas and Capecchi, (1987) Cell51: 503512; Nandi et al. (1988) Proc. Natl. Acad. Sci. USA 85:3845-3849;and Mansour et al. (1988) Nature 336:348-352; Evans and Kaufman, (1981)Nature 294:146-154; Doetschman et al. (1987) Nature 330:576-578; Thomaand Capecchi, (1987) Cell 51:503-512; Thompson et al. (1989) Cell56:316-321.

Random Insertion

In one embodiment, the DNA encoding the transgene sequences can berandomly inserted into the chromosome of a cell. The random integrationcan result from any method of introducing DNA into the cell known to oneof skill in the art. This may include, but is not limited to,electroporation, sonoporation, use of a gene gun, lipotransfection,calcium phosphate transfection, use of dendrimers, microinjection, theuse of viral vectors including adenoviral, AAV, and retroviral vectors,and group II ribozymes. In one embodiment, the DNA encoding the can bedesigned to include a reporter gene so that the presence of thetransgene or its expression product can be detected via the activationof the reporter gene. Any reporter gene known in the art can be used,such as those disclosed above. By selecting in cell culture those cellsin which the reporter gene has been activated, cells can be selectedthat contain the transgene. In other embodiments, the DNA encoding thetransgene can be introduced into a cell via electroporation. In otherembodiments, the DNA can be introduced into a cell via lipofection,infection, or transformation. In one embodiment, the electroporationand/or lipofection can be used to transfect fibroblast cells. In aparticular embodiment, the transfected fibroblast cells can be used asnuclear donors for nuclear transfer to generate transgenic animals asknown in the art and described below.

Cells that have been stained for the presence of a reporter gene canthen be sorted by FACS to enrich the cell population such that we have ahigher percentage of cells that contain the DNA encoding the transgeneof interest. In other embodiments, the FACS-sorted cells can then becultured for a periods of time, such as 12, 24, 36, 48, 72, 96 or morehours or for such a time period to allow the DNA to integrate to yield astable transfected cell population.

Vectors for Producing Transgenic Animals

Nucleic acid targeting vector constructs can be designed to accomplishhomologous recombination in cells. In one embodiment, a targeting vectoris designed using a “poly(A) trap”. Unlike a promoter trap, a poly(A)trap vector captures a broader spectrum of genes including those notexpressed in the target cell (i.e fibroblasts or ES cells). A polyA trapvector includes a constitutive promoter that drives expression of aselectable marker gene lacking a polyA signal. Replacing the polyAsignal is a splice donor site designed to splice into downstream exons.In this strategy, the mRINA of the selectable marker gene can bestabilized upon trapping of a polyA signal of an endogenous generegardless of its expression status in the target cells. In oneembodiment, a targeting vector is constructed including a selectablemarker that is deficient of signals for polyadenylation.

These targeting vectors can be introduced into mammalian cells by anysuitable method including, but not limited, to transfection,transformation, virus-mediated transduction, or infection with a viralvector. In one embodiment, the targeting vectors can contain a 3′recombination arm and a 5′ recombination arm (i.e. flanking sequence)that is homologous to the genomic sequence of interest. The 3′ and 5′recombination arms can be designed such that they flank the 3′ and 5′ends of at least one functional region of the genomic sequence. Thetargeting of a functional region can render it inactive, which resultsin the inability of the cell to produce functional protein. In anotherembodiment, the homologous DNA sequence can include one or more intronand/or exon sequences. In addition to the nucleic acid sequences, theexpression vector can contain selectable marker sequences, such as, forexample, enhanced Green Fluorescent Protein (eGFP) gene sequences,initiation and/or enhancer sequences, poly A-tail sequences, and/ornucleic acid sequences that provide for the expression of the constructin prokaryotic and/or eukaryotic host cells. The selectable marker canbe located between the 5′ and 3′ recombination arm sequence.

Modification of a targeted locus of a cell can be produced byintroducing DNA into the cells, where the DNA has homology to the targetlocus and includes a marker gene, allowing for selection of cellscomprising the integrated construct. The homologous DNA in the targetvector will recombine with the chromosomal DNA at the target locus. Themarker gene can be flanked on both sides by homologous DNA sequences, a3′ recombination arm and a 5′ recombination arm. Methods for theconstruction of targeting vectors have been described in the art, see,for example, Dai et al., Nature Biotechnology 20: 251-255, 2002; WO00/51424.

A variety of enzymes can catalyze the insertion of foreign DNA into ahost genome. Viral integrases, transposases and site-specificrecombinases mediate the integration of virus genomes, transposons orbacteriophages into host genomes. An extensive collection of enzymeswith these properties can be derived from a wide variety of sources.Retroviruses combine several useful features, including the relativesimplicity of their genomes, ease of use and their ability to integrateinto the host cell genome, permitting long-term transgene expression inthe transduced cells or their progeny. They have, therefore, been usedin a large number of gene-therapy protocols. Vectors based on Lentivirusvectors, have been attractive candidates for both gene therapy andtransgenic applications as have sdeno-associated virus, which is a smallDNA virus (parvovirus) that is co-replicated in mammalian cells togetherwith helper viruses such as adenovirus, herpes simplex virus or humancytomegalovirus. The viral genome essentially consists of only two ORFs(rep, a non-structural protein, and cap, a structural protein) fromwhich (at least) seven different polypeptides are derived by alternativesplicing and alternative promoter usage. In the presence of ahelper-virus, the rep proteins mediate replication of the AAV genome.Integration, and thus a latent virus infection, occurs in the absence ofhelper virus. Transposons are also of interest. These are segments ofmobile DNA that can be found in a variety of organisms. Although activetransposons are found in many prokaryotic systems and insects, nofunctional natural transposons exist in vertebrates. The Drosophila Pelement transposon has been used for many years as a genome engineeringtool. The sleeping beauty transposon was established from nonfunctionaltransposon copies found in salmonid fish and is significantly moreactive in mammalian cells than prokaryotic or insect transposons.Site-specific recombinases are enzymes that catalyze DNA strand exchangebetween DNA segments that possess only a limited degree of sequencehomology. They bind to recognition sequences that are between 30 and 200nucleotides in length, cleave the DNA backbone, exchange the two DNAdouble helices involved and religate the DNA. In some site-specificrecombination systems, a single polypeptide is sufficient to perform allof these reactions, whereas other recombinases require a varying numberof accessory proteins to fulfill these tasks. Site-specific recombinasescan be clustered into two protein families with distinct biochemicalproperties, namely tyrosine recombinases (in which the DNA is covalentlyattached to a tyrosine residue) and serine recombinases (where covalentattachment occurs at a serine residue). The most popular enzymes usedfor genome modification approaches are Cre (a tyrosine recombinasederived from E. coli bacteriophage P1) and fC31 integrase (a serinerecombinase derived from the Streptomyces phage fC31). Several otherbacteriophage derived site-specific recombinases (including Flp, lambdaintegrase, bacteriophage HK022 recombinase, bacteriophage R4 integraseand phage TP901-1 integrase) have been used successfully to mediatestable gene insertions into mammalian genomes. Recently, a site-specificrecombinase has been purified from the Streptomyces bacteriophage. ThefC31 recombinase is a member of the resolvase family and mediates phageintegration. In this process the bacteriophage attP site recombines withthe corresponding attB site in the bacterial genome. The crossovergenerates two sites, attL and attR, which are no longer a target forrecombinase action, in the absence of accessory proteins. The reactionalso takes place in mammalian cells and can therefore be used to mediatesite-specific integration of therapeutic genes. The site-specificity oftyrosine-recombinases has been difficult to modify by direct proteinengineering because the catalytic domain and the DNA recognition domainare closely interwoven. Therefore, changes in specificity are oftenaccompanied by a loss in activity. Serine recombinases might be moreamenable to engineering and a hyperactive derivative of TO resolvase hasbeen modified by exchange of the natural DBD for a zinc-finger domain ofthe human zinc-finger transcription factor Zif268. The DNAsite-specificity of the resulting chimeric protein, termed Z-resolvase,had been switched to that of Zif268. Zinc-finger proteins can bemodified by in vitro protein evolution to recognize any DNA sequence,therefore, this approach could enable development of chimericrecombinases that can integrate therapeutic genes into precise genomiclocations. Methods for enhancing or mediating recombination include thecombination of site-specific recombination and homologous recombination,AAV-vector mediated, and zinc-finger nuclease mediated recombination(ref: Geurts et. al., Science, 325: 433, 2009)

The term “vector,” as used herein, refers to a nucleic acid molecule(preferably DNA) that provides a useful biological or biochemicalproperty to an inserted nucleic acid. “Expression vectors” according tothe invention include vectors that are capable of enhancing theexpression of one or more molecules that have been inserted or clonedinto the vector, upon transformation of the vector into a cell. Examplesof such expression vectors include, phages, autonomously replicatingsequences (ARS), centromeres, and other sequences which are able toreplicate or be replicated in vitro or in a cell, or to convey a desirednucleic acid segment to a desired location within a cell of an animal.Expression vectors useful in the present invention include chromosomal-,episomal- and virus-derived vectors, e.g., vectors derived frombacterial plasmids or bacteriophages, and vectors derived fromcombinations thereof, such as cosmids and phagemids or virus-basedvectors such as adenovirus, AAV, lentiviruses. A vector can have one ormore restriction endonuclease recognition sites at which the sequencescan be cut in a determinable fashion without loss of an essentialbiological function of the vector, and into which a nucleic acidfragment can be spliced in order to bring about its replication andcloning. Vectors can further provide primer sites, e.g., for PCR,transcriptional and/or translational initiation and/or regulation sites,recombinational signals, replicons, selectable markers, etc. Clearly,methods of inserting a desired nucleic acid fragment which do notrequire the use of homologous recombination, transpositions orrestriction enzymes (such as, but not limited to, UDG cloning of PCRfragments (U.S. Pat. No. 5,334,575), TA Cloning® brand PCR cloning(Invitrogen Corp., Carlsbad, Calif.)) can also be applied to clone anucleic acid into a vector to be used according to the presentinvention.

Cells homozygous at a targeted locus can be produced by introducing DNAinto the cells, where the DNA has homology to the target locus andincludes a marker gene, allowing for selection of cells comprising theintegrated construct. The homologous DNA in the target vector willrecombine with the chromosomal DNA at the target locus. The marker genecan be flanked on both sides by homologous DNA sequences, a3′recombination arm and a 5′ recombination arm. Methods for theconstruction of targeting vectors have been described in the art, see,for example, Dai et al. (2002) Nature Biotechnology 20: 251-255; WO00/51424, FIG. 6; and Gene Targeting: A Practical Approach. Joyner, A.Oxford University Press, USA; 2nd ed. Feb. 15, 2000.

Various constructs can be prepared for homologous recombination at atarget locus. Usually, the construct can include at least 25 bp, 50 bp,100 bp, 500 bp, 1 kbp, 2 kbp, 4 kbp, 5 kbp, 10 kbp, 15 kbp, 20 kbp, or50 kbp of sequence homologous with the target locus.

Various considerations can be involved in determining the extent ofhomology of target DNA sequences, such as, for example, the size of thetarget locus, availability of sequences, relative efficiency of doublecross-over events at the target locus and the similarity of the targetsequence with other sequences. The targeting DNA can include a sequencein which DNA substantially isogenic flanks the desired sequencemodifications with a corresponding target sequence in the genome to bemodified. The substantially isogenic sequence can be at least about 95%,97-98%, 99.0-99.5%, 99.6-99.9%, or 100% identical to the correspondingtarget sequence (except for the desired sequence modifications). Thetargeting DNA and the target DNA preferably can share stretches of DNAat least about 75, 150 or 500 base pairs that are 100% identical.Accordingly, targeting DNA can be derived from cells closely related tothe cell line being targeted; or the targeting DNA can be derived fromcells of the same cell line or animal as the cells being targeted.

Suitable selectable marker genes include, but are not limited to: genesconferring the ability to grow on certain media substrates, such as thetk gene (thymidine kinase) or the hprt gene (hypoxanthinephosphoribosyltransferase) which confer the ability to grow on HATmedium (hypoxanthine, aminopterin and thymidine); the bacterial gpt gene(guanine/xanthine phosphoribosyltransferase) which allows growth on MAXmedium (mycophenolic acid, adenine, and xanthine). See Song et al.(1987) Proc. Nat'l Acad. Sci. U.S.A. 84:6820-6824. See also Sambrook etal. (1989) Molecular Cloning—A Laboratory Manual, Cold Spring HarborLaboratory, Cold Spring Harbor, N.Y., see chapter 16. Other examples ofselectable markers include: genes conferring resistance to compoundssuch as antibiotics, genes conferring the ability to grow on selectedsubstrates, genes encoding proteins that produce detectable signals suchas luminescence, such as green fluorescent protein, enhanced greenfluorescent protein (eGFP). A wide variety of such markers are known andavailable, including, for example, antibiotic resistance genes such asthe neomycin resistance gene (neo) (Southern, P., and P. Berg, (1982) J.Mol. Appl. Genet. 1:327-341); and the hygromycin resistance gene (hyg)(Nucleic Acids Research 11:6895-6911 (1983), and Te Riele et al. (1990)Nature 348:649651). Additional reporter genes useful in the methods ofthe present invention include acetohydroxyacid synthase (AHAS), alkalinephosphatase (AP), beta galactosidase (LacZ), beta glucoronidase (GUS),chloramphenicol acetyltransferase (CAT), green fluorescent protein(GFP), red fluorescent protein (RFP), yellow fluorescent protein (YFP),cyan fluorescent protein (CFP), horseradish peroxidase (HRP), luciferase(Luc), nopaline synthase (NOS), octopine synthase (OCS), and derivativesthereof Multiple selectable markers are available that confer resistanceto ampicillin, bleomycin, chloramphenicol, gentamycin, hygromycin,kanamycin, lincomycin, blasticidin, zeocin, methotrexate,phosphinothricin, puromycin, and tetracycline. Methods to determinesuppression of a reporter gene are well known in the art, and include,but are not limited to, fluorometric methods (e.g. fluorescencespectroscopy, Fluorescence Activated Cell Sorting (FACS), fluorescencemicroscopy), antibiotic resistance determination.

Combinations of selectable markers can also be used. To use acombination of markers, the HSV-tk gene can be cloned such that it isoutside of the targeting DNA (another selectable marker could be placedon the opposite flank, if desired). After introducing the DNA constructinto the cells to be targeted, the cells can be selected on theappropriate antibiotics. Selectable markers can also be used fornegative selection. Negative selection markets generally kill the cellsin which they are expressed either because the expression is per setoxic or produces a catalyst that leads to toxic metabolite, such asHerpes simplex virus Type I thymidine kinase (HSV-tk) or diphtheriatoxin A. Generally, the negative selection marker is incorporated intothe targeting vector so that it is lost following a preciserecombination event. Similarly, conventional selectable markers such asGFP can be used for negative selection using, for example, FACS sorting.

Deletions can be at least about 50 bp, more usually at least about 100bp, and generally not more than about 20 kbp, where the deletion cannormally include at least a portion of the coding region including aportion of or one or more exons, a portion of or one or more introns,and can or can not include a portion of the flanking non-coding regions,particularly the 5-non-coding region (transcriptional regulatoryregion). Thus, the homologous region can extend beyond the coding regioninto the 5′-non-coding region or alternatively into the 3-non-codingregion. Insertions can generally not exceed 10 kbp, usually not exceed 5kbp, generally being at least 50 bp, more usually at least 200 bp.

The region(s) of homology can include mutations, where mutations canfurther inactivate the target gene, in providing for a frame shift, orchanging a key amino acid, or the mutation can correct a dysfunctionalallele, etc. Usually, the mutation can be a subtle change, not exceedingabout 5% of the homologous flanking sequences or even a singlenucleotide change such as a point mutation in an active site of an exon.Where mutation of a gene is desired, the marker gene can be insertedinto an intron, so as to be excised from the target gene upontranscription.

Various considerations can be involved in determining the extent ofhomology of target DNA sequences, such as, for example, the size of thetarget locus, availability of sequences, relative efficiency of doublecross-over events at the target locus and the similarity of the targetsequence with other sequences. The targeting DNA can include a sequencein which DNA substantially isogenic flanks the desired sequencemodifications with a corresponding target sequence in the genome to bemodified. The substantially isogenic sequence can be at least about 95%,or at least about 97% or at least about 98% or at least about 99% orbetween 95 and 100%, 9798%, 99.0-99.5%, 99.6-99.9%, or 100% identical tothe corresponding target sequence (except for the desired sequencemodifications). In a particular embodiment, the targeting DNA and thetarget DNA can share stretches of DNA at least about 75, 150 or 500 basepairs that are 100% identical. Accordingly, targeting DNA can be derivedfrom cells closely related to the cell line being targeted; or thetargeting DNA can be derived from cells of the same cell line or animalas the cells being targeted.

The construct can be prepared in accordance with methods known in theart, various fragments can be brought together, introduced intoappropriate vectors, cloned, analyzed and then manipulated further untilthe desired construct has been achieved. Various modifications can bemade to the sequence, to allow for restriction analysis, excision,identification of probes, etc. Silent mutations can be introduced, asdesired. At various stages, restriction analysis, sequencing,amplification with the polymerase chain reaction, primer repair, invitro mutagenesis, etc. can be employed.

The construct can be prepared using a bacterial vector, including aprokaryotic replication system, e.g. an origin recognizable by E. coli,at each stage the construct can be cloned and analyzed. A marker, thesame as or different from the marker to be used for insertion, can beemployed, which can be removed prior to introduction into the targetcell. Once the vector containing the construct has been completed, itcan be further manipulated, such as by deletion of the bacterialsequences, linearization, introducing a short deletion in the homologoussequence. After final manipulation, the construct can be introduced intothe cell.

Techniques which can be used to allow the DNA or RNA construct entryinto the host cell include calcium phosphate/DNA coprecipitation,microinjection of DNA into the nucleus, electroporation, bacterialprotoplast fusion with intact cells, transfection, lipofection,infection, particle bombardment, sperm mediated gene transfer, or anyother technique known by one skilled in the art. The DNA or RNA can besingle or double stranded, linear or circular, relaxed or supercoiledDNA. For various techniques for transfecting mammalian cells, see, forexample, Keown et al., Methods in Enzymology Vol. 185, pp. 527-537(1990).

The following vectors are provided by way of example. Bacterial: pBs,pQE-9 (Qiagen), phagescript, PsiX174, pBluescript SK, pB5KS, pNH8a,pNH16a, pNH18a, pNH46a (Stratagene); pTrc99A, pKK223-3, pKK233-3,pDR540, pRIT5 (Pharmacia). Eukaryotic: pWLneo, pSv2cat, pOG44, pXT1, pSG(Stratagene) pSVK3, pBPv, pMSG, pSVL (Pharmiacia). Also, any otherplasmids and vectors can be used as long as they are replicable andviable in the host. Vectors known in the art and those commerciallyavailable (and variants or derivatives thereof) can in accordance withthe invention be engineered to include one or more recombination sitesfor use in the methods of the invention. Such vectors can be obtainedfrom, for example, Vector Laboratories Inc., Invitrogen, Promega,Novagen, NEB, Clontech, Boehringer Mannheim, Pharmacia, EpiCenter,OriGenes Technologies Inc., Stratagene, PerkinElmer, Pharmingen, andResearch Genetics. Other vectors of interest include eukaryoticexpression vectors such as pFastBac, pFastBacHT, pFastBacDUAL, pSFV, andpTet-Splice (Invitrogen), pEUK-C1, pPUR, pMAM, pMAMneo, pBI101, pBI121,pDR2, pCMVEBNA, and pYACneo (Clontech), pSVK3, pSVL, pMSG, pCH11O, andpKK232-8 (Pharmacia, Inc.), p3′SS, pXT1, pSG5, pPbac, pMbac, pMClneo,and pOG44 (Stratagene, Inc.), and pYES2, pAC360, pBlueBacHis A, B, andC, pVL1392, pBlueBacIII, pCDM8, pcDNA1, pZeoSV, pcDNA3 pREP4, pCEP4, andpEBVHis (Invitrogen, Corp.) and variants or derivatives thereof.

Other vectors include pUC18, pUC19, pBlueScript, pSPORT, cosmids,phagemids, YAC's (yeast artificial chromosomes), BAC's (bacterialartificial chromosomes), P1 (Escherichia coli phage), pQE70, pQE60, pQE9(quagan), pBS vectors, PhageScript vectors, BlueScript vectors, pNH8A,pNH16A, pNH18A, pNH46A (Stratagene), pcDNA3 (Invitrogen), pGEX, pTrsfus,pTrc99A, pET-5, pET9, pKK223-3, pKK233-3, pDR540, pRIT5 (Pharmacia),pSPORT1, pSPORT2, pCMVSPORT2.0 and pSY-SPORT1 (Invitrogen) and variantsor derivatives thereof. Viral vectors can also be used, such aslentiviral vectors (see, for example, WO 03/059923; Tiscornia et al.PNAS 100:1844-1848 (2003)).

Additional vectors of interest include pTrxFus, pThioHis, pLEX, pTrcHis,pTrcHis2, pRSET, pBlueBacHis2, pcDNA3. 1/His, pcDNA3.1 (−)/Myc-His,pSecTag, pEBVHi5, pPIC9K, pPIC3.5K, pAO81S, pPICZ, pPICZA, pPICZB,pPICZC, pGAPZA, pGAPZB, pGAPZC, pBlueBac4.5, pBlueBacHis2, pMelBac,pSinReps, pSinHis, pllD, pND(SP 1), pVgRXR, pcDNA2.1, pYES2, pZErO1.1,pZErO-2.1, pCR-Blunt, pSE280, pSE380, pSE420, pVL1392, pVL1393, pCDM8,pcDNA1.1, pcDNA 1.1/Amp, pcDNA3. 1, pcDNA3. 1/Zeo, pSe, SV2, pRc/CMV2,pRc/RSV, pREP4, pREP7, pREP8, pREP9, pREP 10, pCEP4, pEBVHis, pCR3.1,pCR2.1, pCR3.1-Uni, and pCRBac from Invitrogen; λ, ExCell, λ, gt11,pTrc99A, pKK223-3, pGEX-1 λ T, pGEX-2T, pGEX-2TK, pGEX-4T-1, pGEX-4T-2,pGEX-4T-3, pGEX-3X, pGEX-5X-1, pGEX-5X-2, pGEX-5X-3, pEZZ18, pRIT2T,pMC1871, pSVK3, pSVL, pMSG, pCH110, pKK232-8, pSL1180, pNEO, and pUC4Kfrom Pharmacia; pSCREEN-lb(+), pT7Blue(R), pT7Blue-2, pCITE-4abc(+),pOCUS-2, pTAg, pET32L1C, pET-30LIC, pBAC-2cp LIC, pBACgus-2cp LIC,pT7Blue-2 LIC, pT7Blue-2, λ SCREEN-1, λ BlueSTAR, pET-3abcd, pET-7abc,pET9abcd, pET1 labcd, pET12abc, pET-14b, pET-15b, pET-16b,pET-17b-pET-17xb, pET-19b, pET-20b(+), pET-21abcd(+), pET-22b(+),pET-23abcd(+), pET-24abcd(+), pET-25b(+), pET26b(+), pET-27b(+),pET-28abc(+), pET-29abc(+), pET-30abc(+), pET-31b(+), pET-32abc(+),pET-33b(+), pBAC-1, pBACgus-1, pBAC4x-1, pBACgus4x-1, pBAC-3cp,pBACgus-2cp, pBACsurf-1, plg, Signal plg, pYX, Selecta Vecta-Neo,Selecta VectaHyg, and Selecta Vecta-Gpt from Novagen; pLexA, pB42AD,pGBT9, pAS2-1, pGAD424, pACT2, pGAD GL, pGAD GH, pGAD10, pGilda, pEZM3,pEGFP, pEGFP-1, pEGFP-N, pEGFP-C, pEBFP, pGFPuv, pGFP, p6xHis-GFP,pSEAP2Basic, pSEAP2-Contral, pSEAP2-Promoter, pSEAP2-Enhancer,pβgal-Basic, pβgalControl, pβgal-Promoter, pβgal-Enhancer, pCMV,pTet-Off, pTet-On, pTK-Hyg, pRetro-Off, pRetro-On, pIRESlneo, pIRESihyg,pLXSN, pLNCX, pLAPSN, pMAMneo, pMAMneo-CAT, pMAMneo-LUC, pPUR, pSV2neo,pYEX4T-1/2/3, pYEX-S1, pBacPAK-His, pBacPAK8/9, pAcUW3 1, BacPAK6,pTriplEx, λgt10, λgt11, pWE15, and λTriplEx from Clontech; Lambda ZAPII, pBK-CMV, pBK-RSV, pBluescript II KS +/−, pBluescript II SK +/−,pAD-GAL4, pBD-GAL4 Cam, pSurfscript, Lambda FIX II, Lambda DASH, LambdaEMBL3, Lambda EMBL4, SuperCos, pCR-Scrigt Amp, pCR-Script Cam,pCR-Script Direct, pBS +/1−, pBC KS +/−, pBC SK +/−, Phagescript,pCAL-n-EK, pCAL-n, pCAL-c, pCAL-kc, pET-3abcd, pET-11abcd, pSPUTK,pESP-1, pCMVLacI, pOPRSVI/MCS, pOPI3 CAT, pXT1, pSG5, pPbac, pMbac,pMClneo, pMClneo Poly A, pOG44, pOG45, pFRTβGAL, pNEOβGAL, pRS403,pRS404, pRS405, pRS406, pRS413, pRS414, pRS415, and pRS416 fromStratagene.

Additional vectors include, for example, pPC86, pDBLeu, pDBTrp, pPC97,p2.5, pGAD1-3, pGAD10, pACt, pACT2, pGADGL, pGADGH, pAS2-1, pGAD424,pGBT8, pGBT9, pGAD-GAL4, pLexA, pBD-GAL4, pHISi, pHISi-1, placZi,pB42AD, pDG202, pJK202, pJG4-5, pNLexA, pYESTrp and variants orderivatives thereof.

Promoters

Vector constructs used to produce the animals of the invention caninclude regulatory sequences, including, for example, a promoter,operably linked to the sequence. Large numbers of suitable vectors andpromoters are known to those of skill in the art, and are commerciallyavailable.

In specific embodiments, the present invention provides animals, tissuesand cells that express a transgene, and in particular an immunomodulatoror anticoagulant transgene, in pancreatic tissue. To target expressionto a particular tissue, the animal is developed using a vector thatincludes a promoter specific for pancreatic gene expression.

In one embodiment, the nucleic acid construct contains a regulatorysequence operably linked to the transgene sequence to be expressed. Inone embodiment, the regulatory sequence can be a promoter sequence. Inone embodiment, the promoter can be a regulatable promoter. In suchsystems, drugs, for example, can be used to regulate whether the peptideis expressed in the animal, tissue or organ. For example, expression canbe prevented while the organ or tissue is part of the pig, butexpression induced once the pig has been transplanted to the human for aperiod of time to overcome the cellular immune response. In addition,the level of expression can be controlled by a regulatable promotersystem to ensure that immunosuppression of the recipient's immune systemdoes not occur. The regulatable promoter system can be selected from,but not limited to, the following gene systems: a metallothioneinpromoter, inducible by metals such as copper (see Lichtlen andSchaffner, Swiss Med Wkly., 2001, 131 (45-46):647-52); atetracycline-regulated system (see Imhof et al., J Gene Med., 2000,2(2):107-16); an ecdysone-regulated system (see Saez et al., Proc NatlAcad Sci USA., 2000, 97(26):14512-7); a cytochrome P450 induciblepromoter, such as the CYP1A1 promoter (see Fujii-Kuriyama et al., FASEBJ., 1992, 6(2):70610); a mifepristone inducible system (see Sirin andPark, Gene., 2003, 323:67-77); a coumarin-activated system (see Zhao etal., Hum Gene Ther., 2003, 14(17): 1619-29); a macrolide induciblesystem (responsive to macrolide antibiotics such as rapamycin,erythromycin, clarithromycin, and roxitiromycin) (see Weber et al., NatBiotechnol., 2002, 20(9):901-7; Wang et al., Mol Ther., 2003,7(6):790-800); an ethanol induced system (see Garoosi et al., J ExpBot., 2005, 56(416):163542; Roberts et al., Plant Physiol., 2005,138(3):1259-67); a streptogramin inducible system (see Fussenegger etal., Nat Biotechnol., 2000 18(11):1203-8) an electrophile induciblesystem (see Zhu and Fahl, Biochem Biophys Res Commun., 2001,289(1):212-9); and a nicotine inducible system (see Malphettes et al.,Nucleic Acids Res., 2005, 33(12):e107).

In particular embodiments, the promoter is a tissue specific promoter,in particular in expression of an anticoagulant or immunosuppressant.The tissue specific promoter is most preferably a pancreas-specificpromoters (Edlund et al., Science, 1985, 230:912-916). In oneembodiment, the tissue-specific promoter is ins2 (Lomedico P et al.,Cell, 1979, 18:545; GenBank J00747 and J00748.

In other embodiments an enhancer element is used in the nucleic acidconstruct to facilitate increased expression of the transgene in atissue-specific manner. Enhancers are outside elements that drasticallyalter the efficiency of gene transcription (Molecular Biology of theGene, Fourth Edition, pp. 708-710, Benjamin Cummings Publishing Company,Menlo Park, Calif. ©1987). In a particular embodiment, the pdx-1enhancer (also known as IPF-1, STF-1, and IDX1 (Gerrish K et al., Mol.Endocrinol., 2004, 18(3): 533; Ohlsson et al., EMBO J. 1993 November,12(11):4251-9; Leonard et al., Mol. Endocrinol., 1993, 7(10):1275-83;Miller et al., EMBO J., 1994, 13(5):1145-56; Serup et al., Proc NatlAcad Sci USA., 1996, 93(17):9015-20; Melloul et al., Diabetes., 2002, 51Suppl 3:S320-5; Glick et al., J Biol Chem., 2000, 275(3):2199-204;GenBank AF334615.)) is used in combination with the ins2 promoter, forpancreas specific expression of the transgene(s). In certainembodiments, the animal expresses a transgene under the control of apromoter in combination with an enhancer element. In particularembodiments, the animal includes a pancreas specific promoter element,such as an insulin promoter, and further includes an enhancer element.In some embodiments, the enhancer element is PDX1. In specificembodiments, the animal, tissue or cell includes the RIP promoter incombination with a PDX 1 enhancer. In other embodiments, the promotercan be a ubiquitous promoter. Ubiquitous promoters include, but are notlimited to the following: viral promoters like CMV, SV40. Suitablepromoters also include beta-Actin promoter, gamma-actin promoter, GAPDHpromoters, H2K, ubiquitin and the rosa promoter.

Selection of Transgenic Cells

In some cases, the transgenic cells have genetic modifications that arethe result of targeted transgene insertion or integration (i.e. viahomologous recombination) into the cellular genome. In some cases, thetransgenic cells have genetic modification that are the result ofnon-targeted (random) integration into the cellular genome. The cellscan be grown in appropriately-selected medium to identify cellsproviding the appropriate integration. Those cells which show thedesired phenotype can then be further analyzed by restriction analysis,electrophoresis, Southern analysis, polymerase chain reaction, oranother technique known in the art. By identifying fragments which showthe appropriate insertion at the target gene site, (or, in non-targetedapplications, where random integration techniques have produced thedesired result) cells can be identified in which homologousrecombination (or desired non-targeted integration events) has occurredto inactivate or otherwise modify the target gene.

The presence of the selectable marker gene establishes the integrationof the target construct into the host genome. Those cells which show thedesired phenotype can then be further analyzed by restriction analysis,electrophoresis, Southern analysis, polymerase chain reaction, etc toanalyze the DNA in order to establish whether homologous ornon-homologous recombination occurred. This can be determined byemploying probes for the insert and then sequencing the 5′ and 3′regions flanking the insert for the presence of the gene extendingbeyond the flanking regions of the construct or identifying the presenceof a deletion, when such deletion is introduced. Primers can also beused which are complementary to a sequence within the construct andcomplementary to a sequence outside the construct and at the targetlocus. In this way, one can only obtain DNA duplexes having both of theprimers present in the complementary chains if homologous recombinationhas occurred. For example, by demonstrating the presence of the primersequences or the expected size sequence, the occurrence of homologousrecombination is supported.

The polymerase chain reaction used for screening homologousrecombination events is described in Kim and Smithies, (1988) NucleicAcids Res. 16:8887-8903; and Joyner et al. (1989) Nature 338:153-156.

The cell lines obtained from the first round of targeting (or fromnon-targeted (random) integration into the genome) are likely to beheterozygous for the integrated allele. Homozygosity, in which bothalleles are modified, can be achieved in a number of ways. One approachis to grow up a number of cells in which one copy has been modified andthen to subject these cells to another round of targeting (ornon-targeted (random) integration) using a different selectable marker.Alternatively, homozygotes can be obtained by breeding animalsheterozygous for the modified allele. In some situations, it can bedesirable to have two different modified alleles. This can be achievedby successive rounds of gene targeting (or random integration) or bybreeding heterozygotes, each of which carries one of the desiredmodified alleles. In certain embodiments, at least one element of theanimal is derived by selection of a spontaneously occurring mutation inan allele, in particular to develop a homozygous animal. In certainembodiments, a selection technique is used to obtain homologous knockoutcells from heterozygous cells by exposure to very high levels of aselection agent. Such a selection can be, for example, by use of anantibiotic such as geneticin (G418).

Cells that have been transfected or otherwise received an appropriatevector can then be selected or identified via genotype or phenotypeanalysis. In one embodiment, cells are transfected, grown inappropriately-selected medium to identify cells containing theintegrated vector. The presence of the selectable marker gene indicatesthe presence of the transgene construct in the transfected cells. Thosecells which show the desired phenotype can then be further analyzed byrestriction analysis, electrophoresis, Southern analysis, polymerasechain reaction, etc to analyze the DNA in order to verify integration oftransgene(s) into the genome of the host cells. Primers can also be usedwhich are complementary to transgene sequence(s). The polymerase chainreaction used for screening homologous recombination and randomintegration events is known in the art, see, for example, Kim andSmithies, Nucleic Acids Res. 16:8887-8903, 1988; and Joyner et al.,Nature 338:153-156, 1989. The specific combination of a mutant polyomaenhancer and a thymidine kinase promoter to drive the neomycin gene hasbeen shown to be active in both embryonic stem cells and EC cells byThomas and Capecchi, supra, 1987; Nicholas and Berg (1983) inTeratocarcinoma Stem Cell, eds. Siver, Martin and Strikland (Cold SpringHarbor Lab., Cold Spring Harbor, N.Y. (pp. 469-497); and Linney andDonerly, Cell 35:693-699, 1983.

Cells that have undergone homologous recombination can be identified bya number of methods. In one embodiment, the selection method can detectthe absence of an immune response against the cell, for example by ahuman anti-gal antibody. In other embodiments, the selection method caninclude assessing the level of clotting in human blood when exposed to acell or tissue. Selection via antibiotic resistance has been used mostcommonly for screening. This method can detect the presence of theresistance gene on the targeting vector, but does not directly indicatewhether integration was a targeted recombination event or a randomintegration. Alternatively, the marker can be a fluorescent marker genesuch as GFP or RFP, or a gene that is detectable on the cell surface viacell sorting or FACs analysis. Certain technology, such as Poly A andpromoter trap technology, increase the probability of targeted events,but again, do not give direct evidence that the desired phenotype hasbeen achieved. In addition, negative forms of selection can be used toselect for targeted integration; in these cases, the gene for a factorlethal to the cells (e.g. Tk or diptheria A toxin) is inserted in such away that only targeted events allow the cell to avoid death. Cellsselected by these methods can then be assayed for gene disruption,vector integration and, finally, gene depletion. In these cases, sincethe selection is based on detection of targeting vector integration andnot at the altered phenotype, only targeted knockouts, not pointmutations, gene rearrangements or truncations or other suchmodifications can be detected.

Characterization can be further accomplished by the followingtechniques, including, but not limited to: PCR analysis, Southern blotanalysis, Northern blot analysis, specific lectin binding assays, and/orsequencing analysis. Phenotypic characterization can also beaccomplished, including by binding of anti-mouse antibodies in variousassays including immunofluorescence, immunocytochemistry, ELISA assays,flow cytometry, western blotting, testing for transcription of RNA incells such as by RT-PCR.

In other embodiments, GTKO animals or cells contain additional geneticmodifications. Genetic modifications can include more than justhomologous targeting, but can also include random integrations ofexogenous genes, mutations, deletions and insertions of genes of anykind. The additional genetic modifications can be made by furthergenetically modifying cells obtained from the transgenic cells andanimals described herein or by breeding the animals described hereinwith animals that have been further genetically modified. Such animalscan be modified to eliminate the expression of at least one allele ofctGT gene, the CMP-Neu5Ac hydroxylase gene (see, for example, U.S. Pat.No. 7,368,284), the iGb3 synthase gene (see, for example, U.S. PatentPublication No. 2005/0155095), and/or the Forssman synthase gene (see,for example, U.S. Patent Publication No. 2006/0068479). In additionalembodiments, the animals described herein can also contain geneticmodifications to express fucosyltransferase, sialyltransferase and/orany member of the family of glucosyltransferases. To achieve theseadditional genetic modifications, in one embodiment, cells can bemodified to contain multiple genetic modifications. In otherembodiments, animals can be bred together to achieve multiple geneticmodifications. In one specific embodiment, animals, such as pigs,lacking expression of functional immunoglobulin, produced according tothe process, sequences and/or constructs described herein, can be bredwith animals, such as pigs, lacking expression of αGT (for example, asdescribed in WO 04/028243).

In another embodiment, the expression of additional genes responsiblefor xenograft rejection can be eliminated or reduced. Such genesinclude, but are not limited to the CMP-NEUAc Hydroxylase Gene, theisoGloboside 3 Synthase gene, and the Forssman synthase gene.

In addition, genes or eDNA encoding complement related proteins, whichare responsible for the suppression of complement mediated lysis canalso be expressed in the animals and tissues of the present invention.Such genes include, but are not limited to CD59, DAF (CDSS), and CD46(see, for example, WO 99/53042; Chen et al. Xenotransplantation, Volume6 Issue 3 Page 194-August 1999, which describes pigs that expressCD59/DAF transgenes; Costa C et al, Xenotransplantation. 2002 January;9(1):45-57, which describes transgenic pigs that express human CD59 andH-transferase; Zhao L et al.; Diamond L E et al. Transplantation. 2001Jan. 15; 71(1):132-42, which describes a human CD46 transgenic pigs.)

Additional modifications can include expression of compounds, such asantibodies, which down-regulate the expression of a cell adhesionmolecule by the cells, such as described in WO 00/31126, entitled“Suppression of xenograft rejection by down regulation of a celladhesion molecules” and compounds in which co-stimulation by signal 2 isprevented, such as by administration to the organ recipient of a solubleform of CTLA-4 from the xenogeneic donor organism, for example asdescribed in WO 99/57266, entitled “Immunosuppression by blocking T cellco-stimulation signal 2 (B7/CD28 interaction)”.

Nuclear Transfer

Engineered transgenic animals such as ungulates or pigs described hereinmay be produced using any suitable techniques known in the art. Thesetechniques include, but are not limited to, microinjection (e.g., ofpronuclei), sperm-mediated gene transfer, electroporation of ova orzygotes, and/or nuclear transplantation.

In certain embodiments, sperm mediated gene transfer can be used toproduce the genetically modified ungulates described herein. The methodsand compositions described herein to insert transgenes can be used togenetically modify sperm cells via any technique described herein orknown in the art. The genetically modified sperm can then be used toimpregnate a female recipient via artificial insemination,intracytoplasmic sperm injection or any other known technique. In oneembodiment, the sperm and/or sperm head can be incubated with theexogenous nucleic acid for a sufficient time period. Sufficient timeperiods include, for example, about 30 seconds to about 5 minutes,typically about 45 seconds to about 3 minutes, more typically about 1minute to about 2 minutes.

The potential use of sperm cells as vectors for gene transfer was firstsuggested by Brackeff et al., Proc., Natl. Acad. Sci. USA 68:353-357(1971). This was followed by reports of the production of transgenicmice and pigs after in vitro fertilization of oocytes with sperm thathad been incubated by naked DNA (see, for example, Lavitrano et al.,Cell 57:717-723 (1989) and Gandolfi et al. Journal of Reproduction andFertility Abstract Series 4, 10 (1989)), although other laboratorieswere not able to repeat these experiments (see, for example, Brinster etal. Cell 59:239-241 (1989) and Gavora et al., Canadian Journal of AnimalScience 71:287-291 (1991)). Since then, successful sperm mediated genetransfer has been achieved in chicken (see, for example, Nakanishi andIritani, Mol. Reprod. Dev. 36:258-261 (1993)); mice (see, for example,Maione, Mol. Reprod. Dev. 59:406 (1998)); and pigs (see, for example,Lavitrano et al. Transplant. Proc. 29:3508-3509 (1997); Lavitrano etal., Proc. Natl. Acad. Sci. USA 99:14230-5 (2002); Lavitrano et al.,Mol. Reprod. Dev. 64-284-91 (2003)). Similar techniques are alsodescribed in U.S. Pat. No. 6,376,743; issued Apr. 23, 2002; U.S. PatentPublication Nos. 20010044937, published Nov. 22, 2001, and 20020108132,published Aug. 8, 2002).

In some embodiments, intracytoplasmic sperm injection can be used toproduce the genetically modified ungulates described herein. This can beaccomplished by coinserting an exogenous nucleic acid and a sperm intothe cytoplasm of an unfertilized oocyte to form a transgenic fertilizedoocyte, and allowing the transgenic fertilized oocyte to develop into atransgenic embryo and, if desired, into a live offspring. The sperm canbe a membrane-disrupted sperm head or a demembranated sperm head. Thecoinsertion step can include the substep of preincubating the sperm withthe exogenous nucleic acid for a sufficient time period, for example,about 30 seconds to about 5 minutes, typically about 45 seconds to about3 minutes, more typically about 1 minute to about 2 minutes. Thecoinsertion of the sperm and exogenous nucleic acid into the oocyte canbe via microinjection. The exogenous nucleic acid mixed with the spermcan contain more than one transgene, to produce an embryo that istransgenic for more than one transgene as described herein. Theintracytoplasmic sperm injection can be accomplished by any techniqueknown in the art, see, for example, U.S. Pat. No. 6,376,743.

Any additional technique known in the art may be used to introduce thetransgene into animals. Such techniques include, but are not limited topronuclear microinjection (see, for example, Hoppe, P. C. and Wagner, T.E., 1989, U.S. Pat. No. 4,873,191); retrovirus mediated gene transferinto germ lines (see, for example, Van der Putten et al., 1985, Proc.Natl. Acad. Sci., USA 82:6148-6152); gene targeting in embryonic stemcells (see, for example, Thompson et al., 1989, Cell 56:313-321;Wheeler, M. B., 1994, WO 94/26884); electroporation of embryos (see, forexample, Lo, 1983, Mol Cell. Biol. 3:1803-1814); cell gun; transfection;transduction; retroviral infection; adenoviral infection;adenoviral-associated infection; liposome-mediated gene transfer; nakedDNA transfer; and sperm-mediated gene transfer (see, for example,Lavitrano et al., 1989, Cell 57:717-723); etc. For a review of suchtechniques, see, for example, Gordon, 1989, Transgenic Anithals, Intl.Rev. Cytol. 115:171-229. In particular embodiments, the expression ofCTLA4 and/or CTLA4-Ig fusion genes in ungulates can be accomplished viathese techniques.

In one embodiment, microinjection of the constructs encoding thetransgene can be used to produce the transgenic animals. In oneembodiment, the nucleic acid construct or vector can be microinjectioninto the pronuclei of a zygote. In one embodiment, the construct orvector can be injected into the male pronuclei of a zygote. In anotherembodiment, the construct or vector can be injected into the femalepronuclei of a zygote. In a further embodiment, the construct or vectorcan be injected via sperm-mediated gene transfer.

Microinjection of the transgene construct or vector can include thefollowing steps: superovulation of a donor female; surgical removal ofthe egg, fertilization of the egg; injection of the transgenetranscription unit into the pronuclei of the embryo; and introduction ofthe transgenic embryo into the reproductive tract of a pseudopregnanthost mother, usually of the same species. See for example U.S. Pat. No.4,873,191, Brinster, et al. 1985. PNAS 82:4438; Hogan, et al., in“Manipulating the Mouse Embryo: A Laboratory Manual”. Cold Spring HarborLaboratory, Cold Spring Harbor, N.Y., 1986. Robertson, 1987, inRobertson, ed. “Teratocarcinomas and Embryonic Stem Cells a PracticalApproach” IRL Press, Evnsham. Oxford, England. Pedersen, et al., 1990.“Transgenic Techniques in Mice—A Video Guide”, Cold Spring HarborLaboratory, Cold Spring Harbor, N.Y. Transgenic pigs are routinelyproduced by the microinjection of a transgene construct or vector intopig embryos. In one embodiment, the presence of the transgene can bedetected by isolating genomic DNA from tissue from the tail of eachpiglet and subjecting about 5 micrograms of this genomic DNA to nucleicacid hybridization analysis with a transgene specific probe. In aparticular embodiment, transgenic animals can be produced according toany method known to one skilled in the art, for example, as disclosed inBleck et al., J. Anim. Sci., 76:3072 [1998]; also described in U.S. Pat.Nos. 6,872,868; 6,066,725; 5,523,226; 5,453,457; 4,873,191; 4,736,866;and/or PCT Publication No. WO/9907829.

In one embodiment, the pronuclear microinjection method can includelinking at least approximately 50, 100, 200, 300, 400 or 500 copies ofthe transgenecontaining construct or vector of the present invention toa promoter of choice, for example, as disclosed herein, and then theforeign DNA can be injected through a fine glass needle into fertilizedeggs. In one embodiment, the DNA can be injected into the malepronucleus of the zygote. Pig zygotes are opaque and visualization ofnuclear structures can be difficult. In one embodiment, the pronuclei ornuclei of pig zygotes can be visualized after centrifugation, forexample, at 15000 g for 3 mm. The injection of the pronucleus can becarried out under magnification and use of standard microinjectionapparatus. The zygote can be held by a blunt holding pipette and thezona pellucida, plasma membrane and pronuclear envelope can bepenetrated by an injection pipette. The blunt holding pipette can have asmall diameter, for example, approximately 50 um. The injection pipettecan have a smaller diameter than the holding pipette, for example,approximately 15 um. DNA integration occurs during replication as arepair function of the host DNA. These eggs, containing the foreign DNA,can then be implanted into surrogate mothers for gestation of the embryoaccording to any technique known to one skilled in the art.

In some embodiments, pronuclear microinjection can be performed on thezygote 12 hours post fertilization. Uptake of such genes can be delayedfor several cell cycles. The consequence of this is that depending onthe cell cycle of uptake, only some cell lineages may carry thetransgene, resulting in mosaic offspring. If desired, mosaic animals canbe bred to form true germline transgenic animals.

In other embodiments, ungulate cells such as porcine cells containingtransgenes can be used as donor cells to provide the nucleus for nucleartransfer into enucleated oocytes to produce cloned, transgenic animals.In one embodiment, the ungulate cell need not express the transgeneprotein in order to be useful as a donor cell for nuclear transfer. Inone embodiment, the porcine cell can be engineered to express atransgene from a nucleic acid construct or vector that contains apromoter. Alternatively, the porcine cells can be engineered to expresstransgene under control of an endogenous promoter through homologousrecombination. In one embodiment, the transgene nucleic acid sequencecan be inserted into the genome under the control of a tissue specificpromoter, tissue specific enhancer or both. In another embodiment, thetransgene nucleic acid sequence can be inserted into the genome underthe control of a ubiquitous promoter. In certain embodiments, targetingvectors are provided, which are designed to allow targeted homologousrecombination in somatic cells. These targeting vectors can betransformed into mammalian cells to target the endogenous genes ofinterest via homologous recombination. In one embodiment, the targetingconstruct inserts both the transgene nucleotide sequence and aselectable maker gene into the endogenous gene so as to be in readingframe with the upstream sequence and produce an active fusion protein.Cells can be transformed with the constructs using the methods of theinvention and are selected by means of the selectable marker and thenscreened for the presence of recombinants.

The present invention provides a method for cloning an ungulate such asa pig containing certain transgenes via somatic cell nuclear transfer.In general, the pig can be produced by a nuclear transfer processcomprising the following steps: obtaining desired differentiated pigcells to be used as a source of donor nuclei; obtaining oocytes from apig; enucleating said oocytes; transferring the desired differentiatedcell or cell nucleus into the enucleated oocyte, e.g., by fusion orinjection, to form nuclear transfer (NT) units; activating the resultantNT unit; and transferring said cultured NT unit to a host pig such thatthe NT unit develops into a fetus.

Nuclear transfer techniques or nuclear transplantation techniques areknown in the art (see, for example, Dai et al. Nature Biotechnology20:251-255; Polejaeva et al Nature 407:86-90 (2000); Campbell, et al.,Theriogenology 68 Suppl 1:S214-3 1 (2007); Vajta, et al., Reprod FertilDev 19(2): 403-23 (2007); Campbell et al. (1995) Theriogenology, 43:181;Collas et al. (1994) Mol. Report Dev., 38:264-267; Keefer et al. (1994)Biol. Reprod., 50:935-939; Sims et al. (1993) Proc. Natl. Acad. Sci.,USA, 90:6143-6147; WO 94/26884; WO 94/24274, and WO 90/03432, U.S. Pat.Nos. 4,944,384, 5,057,420, WO 97/07669, WO 97/07668, WO 98/30683, WO00/22098, WO 004217, WO 00/51424, WO 031055302, WO 03/005810, U.S. Pat.Nos. 6,147,276, 6,215,041, 6,235,969, 6,252,133, 6,258,998, 5,945,577,6,525,243, 6,548,741, and Phelps et al. (Science 299:411-414 (2003)).

A donor cell nucleus, which has been modified to contain a transgene ofthe present invention, is transferred to a recipient porcine oocyte. Theuse of this method is not restricted to a particular donor cell type.The donor cell can be as described in Wilmut et al. (1997) Nature385:810; Campbell et al. (1996) Nature 380:64-66; or Cibelli et al.(1998) Science 280:1256-1258. All cells of normal karyotype, includingembryonic, fetal and adult somatic cells which can be used successfullyin nuclear transfer can in principle be employed. Fetal fibroblasts area particularly useful class of donor cells. Generally suitable methodsof nuclear transfer are described in Campbell et al. (1995)Theriogenology 43:181, Collas et al. (1994) Mol. Reprod. Dev.38:264-267, Keefer et al. (1994) Biol. Reprod. 50:935-939, Sims et al.(1993) Proc. Nat'l. Acad. Sci. USA 90:6143-6147, WO-A-9426884,WO-A-9424274, WO-A9807841, WO-A-9003432, U.S. Pat. No. 4,994,384 andU.S. Pat. No. 5,057,420, Campbell et al., (2007) Theriogenology 68 Suppl1, S214-23 1, Vatja et al., (2007) Reprod Fertil Dev 19, 403-423).Differentiated or at least partially differentiated donor cells can alsobe used. Donor cells can also be, but do not have to be, in culture andcan be quiescent. Nuclear donor cells which are quiescent are cellswhich can be induced to enter quiescence or exist in a quiescent statein vivo. Prior art methods have also used embryonic cell types incloning procedures (see, for example, Campbell et al. (1996) Nature,380:64-68) and Stice et al. (1996) Biol. Reprod., 20 54:100-110). In aparticular embodiment, fibroblast cells, such as porcine fibroblastcells can be genetically modified to contain the transgene of interest.

Methods for isolation of oocytes are well known in the art. Essentially,this can comprise isolating oocytes from the ovaries or reproductivetract of a pig. A readily available source of pig oocytes isslaughterhouse materials. For the combination of techniques such asgenetic engineering, nuclear transfer and cloning, oocytes mustgenerally be matured in vitro before these cells can be used asrecipient cells for nuclear transfer, and before they can be fertilizedby the sperm cell to develop into an embryo. This process generallyrequires collecting immature (prophase I) oocytes from mammalianovaries, e.g., bovine ovaries obtained at a slaughterhouse, and maturingthe oocytes in a maturation medium prior to fertilization or enucleationuntil the oocyte attains the metaphase II stage, which in the case ofbovine oocytes generally occurs about 18-24 hours post-aspiration and inthe case of porcine generally occurs at about 35-55 hours. This periodof time is known as the maturation period.”

A metaphase II stage oocyte can be the recipient oocyte, at this stageit is believed that the oocyte can be or is sufficiently “activated” totreat the introduced nucleus as it does a fertilizing sperm. MetaphaseII stage oocytes, which have been matured in vivo have been successfullyused in nuclear transfer techniques. Essentially, mature metaphase IIoocytes can be collected surgically from either nonsuperovulated orsuperovulated porcine 35 to 48, or 39-41, hours past the onset of estrusor past the injection of human chorionic gonadotropin (hCG) or similarhormone.

After a fixed time maturation period, the oocytes can be enucleated.Prior to enucleation the oocytes can be removed and placed inappropriate medium, such as HECM or TCM 199 containing 1 milligram permilliliter of hyaluronidase prior to removal of cumulus cells. Thestripped oocytes can then be screened for polar bodies, and the selectedmetaphase II oocytes, as determined by the presence of polar bodies, arethen used for nuclear transfer. Enucleation follows.

Enucleation can be performed by known methods, such as described in U.S.Pat. No. 4,994,384. For example, metaphase II oocytes can be placed ineither HECM, optionally containing 7-10 micrograms per millilitercytochalasin B, for immediate enucleation, or can be placed in asuitable medium, for example an embryo culture medium such as CRlaa,plus 10% estrus cow serum, and then enucleated later, for example notmore than 24 hours later or 16-18 hours later.

Enucleation can be accomplished microsurgically using a micropipette toremove the polar body and the adjacent cytoplasm. The oocytes can thenbe screened to identify those of which have been successfullyenucleated. One way to screen the oocytes is to stain the oocytes with3-10 microgram per milliliter 33342 Hoechst dye in suitable holdingmedium, and then view the oocytes under ultraviolet irradiation for lessthan 10 seconds. The oocytes that have been successfully enucleated canthen be placed in a suitable culture medium, for example, CRlaa plus 10%serum.

A single mammalian cell of the same species as the enucleated oocyte canthen be transferred into the perivitelline space of the enucleatedoocyte used to produce the NT unit. The mammalian cell and theenucleated oocyte can be used to produce NT units according to methodsknown in the art. For example, the cells can be fused by electrofusion.Electrofusion is accomplished by providing a pulse of electricity thatis sufficient to cause a transient breakdown of the plasma membrane.This breakdown of the plasma membrane is very short because the membranereforms rapidly. Thus, if two adjacent membranes are induced tobreakdown and upon reformation the lipid bilayers intermingle, smallchannels can open between the two cells. Due to the thermodynamicinstability of such a small opening, it enlarges until the two cellsbecome one. See, for example, U.S. Pat. No. 4,997,384 by Prather et al.A variety of electrofusion media can be used including, for example,sucrose, mannitol, sorbitol and phosphate buffered solution. Forexample, the fusion media can comprise a 280 milli molar (mlvi) solutionof mannitol, containing 0.05 MM MgCl2 and 0.001 mM CaCl2 (Walker et al.,Cloning and Stem Cells. 2002; 4(2):105-12). Fusion can also beaccomplished using Sendai virus as a fusogenic agent (Graham, WisterInot. Symp. Monogr., 9, 19, 1969). Also, the nucleus can be injecteddirectly into the oocyte rather than using electroporation fusion. See,for example, Collas and Barnes, (1994) Mol. Reprod. Dev., 38:264-267.After fusion, the resultant fused NT units are then placed in a suitablemedium until activation, for example, CRlaa medium. Typically activationcan be effected shortly thereafter, for example less than 24 hourslater, or about 4-9 hours later for bovine NT and 1-4 hours later forporcine NT.

The NT unit can be activated by known methods. Such methods include, forexample, culturing the NT unit at sub-physiological temperature, inessence by applying a cold, or actually cool temperature shock to the NTunit. This can be most conveniently done by culturing the NT unit atroom temperature, which is cold relative to the physiologicaltemperature conditions to which embryos are normally exposed.Alternatively, activation can be achieved by application of knownactivation agents. For example, penetration of oocytes by sperm duringfertilization has been shown to activate prelusion oocytes to yieldgreater numbers of viable pregnancies and multiple genetically identicalcalves after nuclear transfer. Also, treatments such as electrical andchemical shock can be used to activate NT embryos after fusion. See, forexample, U.S. Pat. No. 5,496,720 to Susko-Parrish et al. Additionally,activation can be effected by simultaneously or sequentially byincreasing levels of divalent cations in the oocyte, and reducingphosphorylation of cellular proteins in the oocyte. This can generallybe effected by introducing divalent cations into the oocyte cytoplasm,e.g., magnesium, strontium, barium or calcium, e.g., in the form of anionophore. Other methods of increasing divalent cation levels includethe use of electric shock, treatment with ethanol and treatment withcaged chelators. Phosphorylation can be reduced by known methods, forexample, by the addition of kinase inhibitors, e.g., serine-threoninekinase inhibitors, such as 6-dimethylaminopurine, staurosporine,2-aminopurine, and sphingosine. Alternatively, phosphorylation ofcellular proteins can be inhibited by introduction of a phosphatase intothe oocyte, e.g., phosphatase 2A and phosphatase 2B.

The activated NT units can then be cultured until they reach a suitablesize for transferring to a recipient female, or alternately, they may beimmediately transferred to a recipient female. Culture media suitablefor culturing and maturation of embryos are well known in the art.Examples of known media, which can be used for embryo culture andmaintenance, include Ham's F-10+10% fetal calf serum (FCS), TissueCulture Medium-199 (TCM-199)+10% fetal calf serum,Tyrodes-Albumin-LactatePyruvate (TALP), Dulbecco's Phosphate BufferedSaline (PBS), Eagle's Whitten's media, PZM, NCSU23 and NCSU37. SeeYoshioka K, Suzuki C, Tanaka A, Anas I M, Iwamura S. Biol Reprod. (2002)January; 66(1):112-9 and Petters R M, Wells K D. J Reprod Fertil Suppl.1993; 48:61-73.

Afterward, the cultured NT unit or units can be washed and then placedin a suitable media contained in well plates which can optionallycontain a suitable confluent feeder layer. Suitable feeder layersinclude, by way of example, fibroblasts and epithelial cells. The NTunits are cultured on the feeder layer until the NT units reach a sizesuitable for transferring to a recipient female, or for obtaining cellswhich can be used to produce cell colonies. NT units can be cultureduntil at least about 2 to 400 cells, about 4 to 128 cells, or at leastabout 50 cells. Alternatively, NT units may be immediately transferredto a recipient female.

The methods for embryo transfer and recipient animal management in thepresent invention are standard procedures used in the embryo transferindustry. Synchronous transfers are important for success of the presentinvention, i.e., the stage of the NT embryo is in synchrony with theestrus cycle of the recipient female. See, for example, Siedel, G E.,Jr. (1981) “Critical review of embryo transfer procedures with cattle inFertilization and Embryonic Development in Vitro, L. Mastroianni, Jr.and J. D. Biggers, ed., Plenum Press, New York, N.Y., page 323. Porcineembryo transfer can be conducted according to methods known in the art.For reference, see Youngs et al. “Factors Influencing the Success ofEmbryo Transfer in the Pig,” Theriogenology (2002) 56: 1311-1320.

Production of Islet Related Cells

The pancreas is a gland organ in the digestive and endocrine system ofvertebrates. It is both an endocrine gland producing several importanthormones, including insulin, glucagon, and somatostatin, as well as anexocrine gland, secreting pancreatic juice containing digestive enzymesthat pass to the small intestine. The bulk of the pancreas is composedof pancreatic exocrine cells and their associated ducts. Embedded withinthis exocrine tissue are roughly one million small clusters of cellscalled the Islets of Langerhans, which are the endocrine cells of thepancreas and secrete insulin, glucagon and several other hormones.

The human pancreas contains approximately 1 million islets ofLangerhans. They are small spheroid clusters of cells, distributedthroughout the organ. They vary considerably in size, ranging from tensof cells to several 1000 cells. “Islet cells” include a collective groupof cell types found in an Islet of Langerhans They comprise the A, B, C,D and PP cells, which can be relatively difficult to distinguish usingstandard staining techniques. a cells secrete glucagon (increase glucosein blood), P cells secrete insulin (decrease glucose in blood), 6 cellssecrete somatostatin (regulates/stops a and P cells), and PP cellssecrete pancreatic polypeptide.

In one embodiment, genetically altered pigs are used as donors ofpancreatic tissue, including pancreatic islets and/or islet cells. Thepancreatic tissue or cells derived from such tissue can comprisepancreatic islet cells, or islets, or islet-cell clusters. In particularembodiments, the cells are pancreatic islets. In more particularembodiments, the cells are pancreatic beta cells. In certainembodiments, the cells are insulin-producing. In still furtherembodiments, the cells are islet-like cells. Islet cell clusters caninclude any one or more of alpha, beta, delta, PP or epsilon cells.Generally, alpha cells producing glucagons make up about 15-20% of totalislet cells in native pancreas, beta cells producing insulin and amylinmake up between about 65-80% of islet cells in native pancreas, deltacells producing somatostatin make up about 3-10% of total islet cells innative pancreas, PP cells producing pancreatic polypeptide make up about3-5% of total islet cells in native pancreas and epsilon cells producingghrelin make up<1% of total islet cells in native pancreas (see Elayatet al. (1995). J. Anat. 186: 629-37).http://www.ncbi.nlm.nih.gov/pmc/articles/PMC 1167020/

The donor pigs may be at any stage of development including, but notlimited to, fetal, neonatal, young and adult. In some embodiments, isletcells are isolated from adult porcine transgenic animals. In alternateembodiments, islet cells are isolated from fetal or neonatal porcinetransgenic animals (see e.g. Mandel (1999) J. Mol. Med. 77:155-60;Cardona, et al. (2006) Nat. Med. 12:304-6). The donor pigs may be underthe age of 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 year(s). In one embodiment,the islet cells are isolated from transgenic pigs under the age of 6years. In another embodiment, the islet cells are isolated fromtransgenic pigs under the age of 3 years. The donor pigs may be any agebetween 0 to 2 years, 2 to 4 years, 4 to 6 years, 6 to 8 years, or 8 to10 years. In some cases, the donor pigs is older than 10 years. Inanother embodiment, the islet cells are isolated from newborn to 2 yearold transgenic pigs. In one embodiment, the islets cells are isolatedfrom fetal to 2 year old transgenic pigs. In a particular embodiment,the islets cells are isolated from 6 months old to 2 year old transgenicpigs, and in a more particular embodiment, 7 months old to 1 year oldtransgenic pigs. In one embodiment, the islet cells are isolated from2-3 year old transgenic pigs. In some cases, the donor pig is less than0 year (i.e. a fetus or embryo). Neonatal islets are more hearty andconsistent post-isolation than adult islets, are more resistant tooxidative stress, have significant growth potential (likely from anascent islet stem cell subpopulation), such that they have the abilityto proliferate post-transplantation and engraftment in thetransplantation site. They have the disadvantage that it can take themup to 4-6 weeks to mature enough such that they are producingsignificant levels of insulin, but this is overcome by treatment withexogenous insulin for the period sufficient for the maturation of theneonatal islets. Survival and functional engraftment of neonatal isletscan be determined by measuring porcine-specific c-peptide levels, whichare easily distinguished from any potential endogenous c-peptide.

Adult porcine islets may be isolated according to a modification of themethod described for human islets and further optimized for pigs (Toso,2000; Yonekawa, 2005), as described previously (Bottino, 2002, 2004;Balamurugan, 2003, 2005). Purity can be evaluated after dithizonestaining of islet samples, and expressed as percent of islets/wholetissue (Balamurugan, 2005). Islets can be cultured for 1-3 days prior totransplantation in order to deplete the preparation of contaminatingexocrine tissue. Prior to Tx, pig islets can be counted, and viabilityassessed by double fluorescent calcein-AM and propidium iodide stain(Lorenzo, 1994). It is recommend that islet cell viability be >75% inall preparations, and purity be >80% islets/whole tissue. Functionalproperties of the islets, including dynamic perifusion and viability,can be determined in vitro prior to Tx (Balamurugan, 2006). In someembodiments, transgenic porcine islet cells are cultured in-vitro toexpand, mature, and/or purify them so that they are suitable forgrafting.

In certain embodiments, the donor transgenic pancreatic tissue issurgically removed. Following surgical removal, the donor pancreases aretransferred to a cleanroom facility for further processing in a coldplastic container in 50 ml tubes containing cold Hanks' Balanced SaltSolution (HBSS) with 0.2% human serum albumin (HSA) added. Blood samplesfrom each donor are sent for virology testing and toxoplasma serology.Samples from each organ are kept in a freezer at −80° C. for futuretesting if necessary.

The islet cells may be isolated by standard collagenase digestion of theminced pancreas via the procedure documented by Ricordi et al. (1990),though with some modifications. Using aseptic technique, the glands aredistended with Liberase™ (a mixture of purified enzymes formulated forrapid dissociation of rodent pancreas and maximal recovery of healthy,intact, and functional islets of Langerhans, wherein the targetsubstrates for these enzymes are not fully identified, but are presumedto be collagen and non-collagen proteins, which comprise theintercellular matrix of pancreatic acinar tissue). (1.5 mg/ml), trimmedof excess fat, blood vessels and connective tissue, minced, and digestedat 37 degree C. in a shaking water bath for 15 minutes at 120 rpm. Thedigestion is achieved using lignocaine mixed with the Liberase™.solution to avoid cell damage during digestion. Following the digestionprocess, the cells are passed through a sterile 400 mm mesh into asterile beaker. A second digestion process is used for any undigestedtissue.

Alternatively, Vitacyte collagenase MA (7.5 Wunsch Units/gram ofpancreatic tissue) and Vitacyte BP protease (0.13 mg/gram of pancreatictissue) can be used.

In certain embodiments, Liberase™ (eg; sourced in New Zealand fromRoche) is used rather than collagenase (see “Improved Pig Islet Yieldand Post-Culture Recovery Using Liberase P1 Purified Enzyme Blend”, T JCavanagh et al. Transplantation Proceedings 30, 367 (1998) and in“Significant Progress In Porcine Islets Mass Isolation UtilizingLiberase™ HI For Enzymatic Low-Temperature Pancreas Digestion”, H.Brandhorst et al. Transplantation Vol 68, 355-361 No. 3, Aug. 15, 1999).The digested tissue is washed three times, and seeded into cell culturemedia RPMI 1640 to which is added 2% human serum albumin (HSA), 10mmol/L nicotinamide, and antibiotic (Ciproxin).

To exclude any contamination of the tissue, quality control proceduresare undertaken on cell culture samples after isolation and beforeencapsulation. Three days after isolation, the cell culture is testedfor microbiological contamination by accredited laboratories. Testingfor porcine endogenous retrovirus (PERV) may be undertaken, for example,at the Virology Laboratory, Auckland Hospital.

The islet yield is determined via dithizone (DTZ) staining of the cells.Dithizone is a zinc-chelating agent and a supravital stain thatselectively stains zinc in the islets of Langherhans, producing adistinctive red appearance.

The viability of the islet cells can be determined using acridin orangeand propidium iodide. Acridin orange is a fluorescent stain that readilypasses through all cell membranes to stain the cytoplasm and nucleus.Bright green fluorescence in both the nucleus and cytoplasm on exposureto ultraviolet (UV) light denotes intact live cells. Conversely,propidium iodide is a fluorescent stain that cannot pass through anintact membrane. It emits a bright red fluorescence when exposed to LIVlight, and the presence of propidium iodide in a cell nucleus indicatessevere damage or a dead cell.

Static glucose stimulation (SGS) is used to assess in vitro function ofthe porcine islets by exposing them to low and high concentrations ofglucose and theophylline. Determination of the in vitro insulinsecretory capacity is undertaken on both free islets (after 3 days inculture) and after their subsequent encapsulation.

When immature porcine islet are used, the IgF-1 (Human Insulin-likeGrowth Factor I) can be used in order to induce immature cells to matureto their insulin-producing form. IgF-1 is a potent mitogenic growthfactor that mediates the growth promoting activities of growth hormonepostnatally. Both IgF-1 and IgF-2 are expressed in many cell types andmay have endocrine, autocrine and paracrine functions. The preferredform of IgF-1 is the amino-terminal tripeptide glycineproline-glutamateof IgF-1 (GPE).

The processes by which islets are purified prior to transplantation aretraumatic to these highly specialized tissues. Such trauma can inducenecrosis or apoptosis. Any method to prepare and encapsulate the isletsknown in the state of the art may be used in this invention. Thesetechniques include microencapsulation of individual islets, ormacroencapsulation of multiple islets/pancreas tissue. Examples of theseinclude the following:

U.S. Pat. No. 7,427,415 to Scharp et al., discloses a method ofencapsulating a biological material which includes the steps of: addinga solution which includes a first buffer to the biological material;centrifuging the biological material to form a pelleted biologicalmaterial; removing supernatant; adding a solution which includes aphotoinitiator dye conjugated to a cell adsorbing material to thepelleted biological material; resuspending and incubating the pelletedbiological material with the solution including the photoinitiator dyeconjugated to the cell adsorbing material for an effective amount oftime; centrifugating mixture; removing the solution including thephotoinitiator dye conjugated to the cell adsorbing material;resuspending the pelleted biological material with a second solutionincluding a second buffer; centrifugating and removing the secondbuffer; resuspending and mixing the biological material with aphotoactive polymer solution; and irradiating the resuspended biologicalmaterial with a photoactive polymer solution with an energy source toform an encapsulated biological material. Preferably, the encapsulatedbiological material is a PEG conformal coated islet allograft.

Other procedures have ensured zero warm ischemia (compared with hourswith most human islet preparations), have involved the use ofnicotinamide to enhance successful in vitro explantation, have involvedminimal incubation time with collagenase or Liberase, have involvedswift non-traumatic encapsulation technology, have involved the use ofIgF-1 (or the GPE tripeptide thereof), the use of an anaesthetic such aslignocaine, and the use of an antibiotic such as ciproproxin etc.

U.S. Pat. No. 7,122,177 to Elliott et al. disclosed a method forencapsulating pancreatic islets. Sodium alginate used for this procedureis extracted from raw material sources (seaweed) and prepared in apowdered ultrapure form. The sterile sodium alginate solution (1.6%) isthen utilized at the Diatranz Islet Transplant Centre to manufactureencapsulated islets. Generally each encapsulation involves presentingislets and a suitable alginate solution (usually sodium alginate) into asource of compatible cations thereby to entrap the islets in acation-alginate gel (usually calcium-alginate gel).

The encapsulation procedure involves extruding a mixture of islets andsodium alginate solution (1.6% w/w) through a droplet generating needleinto a bath of gelling cations (calcium chloride). The islets entrappedin the calcium-alginate gel are then coated with positively chargedpoly-L-ornithine followed by an outer coat of alginate (0.05%). Thecentral core of alginate is then liquefied by the addition of sodiumcitrate. Most capsules contain 3 islets and have a diameter of 300 to400 um.

After liquification of the alginate entrapping the islets, the“capsules” are washed, and again coated with alginate which neutralizesany residual change on the poly-L-ornithine coating and prevents directcontact of the poly-L-ornithine with tissues when the entire capsule istransplanted. The encapsulated islets are kept in cell culture, and thenchecked for contamination, insulin release and viability beforetransplantation. They are only released for transplantation if allquality control tests are negative.

U.S. Pat. No. 6,303,355 to Opara discloses a method of treating isolatedliving cells by first culturing the cells in a medium containing atleast one of (or a combination of): an antioxidant, an anti-cytokine, ananti-endotoxin, or an antibiotic. The cells are then microencapsulatedin a biocompatible microcapsule that contains a hydrogel core and asemipermeable outer membrane, to provide a microcapsule containingliving cells therein.

U.S. Pat. No. 5,578,314 to Cochrum et al. discloses a method forproduction of functional cell and tissue transplants coated withmultiple layer coatings of purified alginate gel with uniform minimumthickness. This method can withstand mechanical, chemical or immunedestruction within the host, does not provoke fibrogenic reactionsimpairing the transplants function, and provides a uniform andcontrollable thickness of the coating to allow for free permeability ofnutrients and secretory and waste products. The uniform coating has athickness of between about 20-200 um which would eliminate fibrogenicand/or immune reactions destructive to the transplant's functionalityand provide substantially complete coverage of the biological tissuecore, thus allowing a successful long-term transplantation of thesecells or tissues. Cochrum et al. state that their method is unique inthat stabilization of the first and subsequent coat by polylysine orother polyamino acid or polycation is not required. The method allowsoptionally the formation of a halo layer, providing an intermediatelayer between an inner and outer coating that uniformly covers anexposed area of biological tissue.

Further direction regarding islet cell isolation may be found in thefollowing references: Qi, et al., Human pancreatic islet isolation: PartI: digestion and collection of pancreatic tissue and Part II:purification and culture of human islets, J Vis Exp, 27. May 2009.

Encapsulation of cellular grafts in an immunoisolation membrane devicesuch as a TheraCyte macroencapsulation device can also be used (seeRafael, et al. (2000) Cell Transpl. 9:107-13). Another technique is the“Valdez capsules” as described in Valdes (1998) “BiologicalEncapsulation as a New Model for Preservation of Islets of Langerhans”Transplantation Proceed 30:481. Alginate sheets can also be used forencapsulation as can beta cell embedding. In technique involving theproduction of alginate sheets, an islet sheet is provided as a thinplanar bioartificial endocrine pancreas fabricated by gelling highlypurified alginate and islets of Langerhans. Acellular alginate layersform a uniform immunoprotective barrier to host rejection of theencapsulated cells, with the tissue nourished by passive diffusion fromadjacent host tissue (see Stors, et al. (2006) Ann. NY Ac. Sci.944:252-266).

The transgenic islets may also be co-transplanted with other cells typessuch as sertoli cells or stem cells, including in particular mesenchymalstem cells (see Osiris Inc. http://www.osiristx.coml).

Method of Treatment

The invention described herein encompasses methods of treatment orpreventing diabetes or prediabetes. The methods include, but are notlimited to, administering one or more pancreatic islet cell(s) from adonor animal described herein to a host in need thereof. The method maybe transplantation or, in some cases, xenotransplantation. The donoranimal may be a porcine. The host may be a primate, for example, anon-human primate including, but not limited to, a monkey. The host maybe a human and in some cases, a human with diabetes or pre-diabetes.

One method of the invention is a method of xenotransplantation whereinthe transgenic pancreatic tissues or cells provided herein aretransplanted into a primate and, after the transplant, the primaterequires reduced or no exogenous insulin. In another embodiment, theprimate requires reduced levels or no exogenous insulin post-transplant.It is generally understood that post-transplant refers to the period oftime after the development of a state of normoglycemia (which may take,for example, approximately 4 or 12 weeks). After the transplant, theprimate may require 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or100% less insulin than that required prior to the transplant. After thetransplant, the primate may require about 5% to about 25% less insulinthan that required prior to the transplant. After the transplant, theprimate may require about 25% to about 50% less insulin than thatrequired prior to the transplant. After the transplant, the primate mayrequire about 50% to about 75% less insulin than that required prior tothe transplant. After the transplant, the primate may require about 75%to about 100% less insulin than that required prior to the transplant.After the transplant, the primate may require less than 0.6, 0.5, 0.4,0.3, 0.2, 0.1, 0.05, or 0.01 exogenous units of insulin per kilogram(kg) per day. In one embodiment, the primate after the transplantrequires any number less than about 0.01 to about 0.1 exogenous units ofinsulin per kilogram (kg) per day. In one embodiment, the primate afterthe transplant requires any number less than about 0.1 to about 0.25exogenous units of insulin per kilogram (kg) per day. In one embodiment,the primate after the transplant requires any number less than about0.25 to about 0.5 exogenous units of insulin per kilogram (kg) per day.In one embodiment, the primate after the transplant requires any numberless than about 0.5 to about 0.6 exogenous units of insulin per kilogram(kg) per day. In one embodiment, after the transplant, the primaterequires less than 4 units of insulin/day. In one embodiment, after thetransplant, the primate requires less than 2 units of insulin/day. Inone embodiment, after the transplant, the primate requires no exogenousinsulin In one embodiment, after the transplant, the primate requiresless than 1 IU per kg per day of insulin. In another particularembodiment, the primate requires less than 0.50 IU/kg per day.

The methods of the invention also include methods of xenotransplantationwherein the transgenic pancreatic tissues or cells provided herein aretransplanted into a primate and, after the transplant, the primaterequires minimal or no immunosuppressive therapy. Reduced or noimmunosuppressive therapy includes, but is not limited to, a reduction(or complete elimination of) in dose of the immunosuppressivedrug(s)/agent(s) compared to that required by other methods; a reduction(or complete elimination of) in the number of types of immunosuppressivedrug(s)/agent(s) compared to that required by other methods; a reduction(or complete elimination of) in the duration of immunosuppressiontreatment compared to that required by other methods; and/or a reduction(or complete elimination of) in maintenance immunosuppression comparedto that required by other methods.

The methods of the invention also include methods of xenotransplantationwherein the transgenic pancreatic tissues or cells provided herein aretransplanted into a primate, wherein the IEQ/kg (pancreatic isletequivalents per kg) requirements are reduced compared to other methods.The IEQ/kg required by the novel invention described here may be, but isnot limited to, below about 100,000; 90,000; 80,000; 70,000; 60,000;50,000; 40,000; 30,000; 20,000; 10,000 or 5,000. The IEQ/kg required bythe novel invention described here may be between about 5,000 to about10,000; about 10,000 to about 15,000; about 15,000 to about 20,000;about 20,000 to about 25,000; about 25,000 to about 30,000; about 30,000to about 35,000; about 35,000 to about 40,000; about 40,000 to about45,000; about 45,000 to about 50,000; about 50,000 to about 55,000;about 55,000 to about 60,000; about 60,000 to about 65,000; about 65,000to about 70,000; about 70,000 to about 75,000; about 75,000 to about80,000; about 80,000 to about 85,000; about 85,000 to about 90,000;about 90,000 to about 95,000; about 95,000 to about 100,000. In oneembodiment, the IEQ/kg is below 100,000. In one embodiment, the IEQ/kgis below 50,000. In one embodiment, the IEQ/kg is below 25,000. In oneembodiment, the IEQ/kg is below 10,000.

The methods of the invention also include methods of treating orpreventing diabetes wherein the transgenic pancreatic tissues or cellsprovided herein are transplanted into a primate and, after thetransplant, the primate has some or all functional transplanted islets.The transplanted primate may have more functional transplanted isletswhen compared to the level prior to transplant or when compared to thelevel achieved using other methods. The islets may be characterized asfunctional using any definition known to one of skill in the art,including, but not limited to, the ability to produce insulin, theability to reduce the host's exogenous insulin requirements, and/or theability to produce donor type C-peptide. In one embodiment, isletfunctionality is defined as basal or stimulated porcine C-peptidegreater than 0.3 ng/dl. In one embodiment, islet functionality isdefined as detectable C-peptide in combination with a greater than 50%reduction of exogenous insulin needs, wherein the C-peptide is producedfrom the transplanted material.

The methods of the invention also include methods of treating orpreventing diabetes wherein the transgenic pancreatic tissues or cellsprovided herein are transplanted into a primate and, after thetransplant, the fasting and non-fasting blood glucose levels of theprimate are maintained at normal levels/These normal levels may bemaintained for any length of time, including, but not limited to, atleast about 3, 6, 12, 24, or 36 months after the transplant. In oneembodiment, the normal levels should be maintained for at least 3months. In another embodiment, the normal levels should be maintainedfor at least 6 months. In another embodiment, the normal levels shouldbe maintained for at least 12 months. Normal fasting and non-fastingblood glucose levels for primates, including but not limited to humansand monkeys, are known to one of skill in the art. In a particularembodiment, FBG can be maintained from about 70 to about 100 mg/dL (3.9to 5.5 mmol/L). In another particular embodiment, NFBG can be maintainedat less than about 200 mg/dL.

In some cases, normal levels of glucose are between about 70-130 mg/dlor 3.9-7.2 mmol/l when tested randomly (without regard to fasting ornon-fasting state) and averaged. In some cases, normal levels of glucoseare about between 65-70 mg/dl after fasting. In certain embodiments, theglucose levels after the transplant are maintained at approximately lessthan about 200 mg/dl, 175 mg/dl, 150 mg/dl, 125 mg/dl, 100 mg/dl, 75mg/dl, or 50 mg/dl. In one embodiment, the glucose level after thetransplant and after an overnight fast is below 140 mg/dl and thispost-fast level is achieved at least 1 times per week for at least 1month.

In one embodiment, the mean glucose levels (average of morning andevening levels) after the transplant are about between 2-5 mmol/l orabout between 3-4 mmol/l.

In one embodiment, after the transplant, the primate has adequateglycemic control. In one embodiment, after the transplant, the glycatedhemoglobin level is less than about 8%, 7%, 6%, 5%, 4% or 3%. In aparticular embodiment, the glycated hemoglobin level after thetransplant is less than 6.5%.

The methods of the invention also include methods of treating orpreventing diabetes wherein the transgenic pancreatic tissues or cellsprovided herein are transplanted into a primate and, after thetransplant, the primate successfully passes an intravenous glucosetolerance test. The test can be performed any time after the transplant,for example, but not limited to, at 1, 3, 6 and/or 12 months after thetransplant. In some cases, the results of the test are successful ifsignificant response to glucose in the form of donor (for example,porcine) C-peptide is demonstrated in the absence of a significantresponse of host (for example, primate) C-peptide.

The methods of the invention also include methods of treating orpreventing diabetes wherein the transgenic pancreatic tissues or cellsprovided herein are transplanted into a primate and, after thetransplant, the primate successfully passes an arginine stimulationtest. The test can be performed any time after the transplant, forexample, but not limited to, at 1, 3, 6 and/or 12 months after thetransplant. In some cases, the results of the test are successful ifsignificant response to glucose in the form of donor (for example,porcine) C-peptide is demonstrated in the absence of a significantresponse of host (for example, primate) C-peptide.

The methods of the invention also include methods of xenotransplantationwherein the transgenic pancreatic tissues or cells provided herein aretransplanted into a primate and, after the transplant, donor C-peptidelevels are detectable. In some instances, the donor C-peptide levels areporcine and, in some cases, the porcine C-peptide levels are aboutbetween 0.2 to about 1.0, about between 0.2 to about 0.75, about between0.2 to about 0.65, about between 0.2 to about 0.55, about between 0.2 toabout 0.45, or about between 0.2 to about 0.35 ng/ml. The donor porcinelevels after transplant may be about 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9 or 1.0 ng/ml. In some cases, the donor porcine levels are greaterthan 1.0 ng/ml. In some cases, the donor porcine levels are greater thanzero. In one embodiment, donor porcine C-peptide levels are about 0.5ng/ml.

The methods of the invention also include methods of treating orpreventing diabetes wherein after the transplantation of transgenicpancreatic tissues or cells, histological analysis of the host primateis conducted. In some cases, the histological analysis of the nativepancreas after necropsy indicates reduced, or in one non-limitingexample, no, insulin-positive beta cells. In these cases or in othercases wherein the native pancreas is not examined, the histologicalexamination of the liver or other site of islet transplant indicatesmultiple viable insulin-positive cells.

The methods of the invention also include methods of treating orpreventing diabetes wherein after the transplantation of transgenicpancreatic tissues or cells, there are not numerous, or seriouslife-threatening, complications associated with the transplantprocedure, immunosuppressive regimen, tolerance-inducing regimen, and/orthe encapsulation of the islets.

The methods of the invention also include methods of treating orpreventing diabetes wherein after the transplantation of transgenicpancreatic tissues or cells, the transplant is repeated. The transplantmay be performed twice, three times or more in any one primate. Thetransplants may be conducted at regular intervals to maintainappropriate insulin levels. The transplant may occur once a year. Thetransplant may occur twice a year. The transplant may occur three timesa year. The transplant may occur more than three times a year. Thetransplant may occur at various times over multiple years. Theparameters of any one transplant, including, but not limited to,surgical procedures, delivery methods, donor tissues and/or cells used,immunosuppressive regimens used and the like, may be different or thesame when compared to other transplants performed in the same primate.

In some embodiments, the method reduces the need for administration ofanti-inflammatories to the host. In other embodiments, the methodreduces the need for administration of anticoagulant to the host. Incertain embodiments, the method reduces the need for administration ofimmunosuppressive agents to the host. In some embodiments, the host isadministered an anti-inflammatory agent for less than thirty days, orless than 20 days, or less than 10 days, or less than 5 days, or lessthan 4 days, or less than 3 days, or less than 2 days, or less than oneday after administration of the pancreatic islet cells. In someembodiments, the host is administered an anticoagulant agent for lessthan thirty days, or less than 20 days, or less than 10 days, or lessthan 5 days, or less than 4 days, or less than 3 days, or less than 2days, or less than one day after administration of the pancreatic isletcells. In some embodiments, the host is administered animmunosuppressive agent for less than thirty days, or less than 20 days,or less than 10 days, or less than 5 days, or less than 4 days, or lessthan 3 days, or less than 2 days, or less than one day afteradministration of the pancreatic islet cells.

The recipient (host) may be partially or fully immunosuppressed or notat all at the time of transplant. Immunosuppressive agents/drugs thatmay be used before, during and/or after the time of transplant are anyknown to one of skill in the art and include, but are not limited to,MMF (mycophenolate mofetil (Cellcept)), ATG (antithymocyte globulin),anti-CD 154 (CD40L), alemtuzumab (Campath), CTLA4-Ig(Abatacept/Orencia), belatacept (LEA29Y), sirolimus (Rapimune),tacrolimus (Prograf), daclizumab (Zenapax), basiliximab (Simulect),infliximab (Remicade), cyclosporin, deoxyspergualin, soluble complementreceptor 1, cobra venom, methylprednisolone, FTY720, everolimus,anti-CD154-Ab, leflunomide, anti-IL-2R-Ab, rapamycin, and humananti-CD154 monoclonal antibody. One or more than one immunosuppressiveagents/drugs may be used together or sequentially. One or more than oneimmunosuppressive agents/drugs may be used for induction therapy or formaintenance therapy. The same or different drugs may be used during theinduction and maintenance stages. In one embodiment, daclizumab(Zenapax) is used for induction therapy and tacrolimus (Prograf) andsirolimus (Rapimune) is used for maintenance therapy. In anotherembodiment, daclizumab (Zenapax) is used for induction therapy and lowdose tacrolimus (Prograf) and low dose sirolimus (Rapimune) is used formaintenance therapy. In one embodiment, alemtuzumab (Campath) is usedfor induction therapy. See Teuteberg et al., Am J Transplantation,10(2):382-388. 2010; van der Windt et al., 2009, Am. J. Transplantation9(12):27162726. 2009; Shapiro, The Scientist, 20(5):43. 2006; Shapiro etal., N Engl J Med. 355:1318-1330. 2006. Immunosuppression may also beachieved using non-drug regimens including, but not limited to, wholebody irradiation, thymic irradiation, and full and/or partialsplenectomy. These techniques may also be used in combination with oneor more immunosuppressive drug/agent.

The transgenic pancreatic islet cells may be transplanted using anymeans known in the art, including, but not limited to, introduction viathe recipient organism's portal vein, under the renal capsule, into thesternomastoid muscle, intraperitoneally, in the gastric submucosa, inthe testes, or in the spleen (see Rood et al., Cell Transplantation,15:89-104. 2006; Dufrane and Gianello, Transplantation, 86:753-760.2008; Hering et al., Nature Medicine, published online 19 Feb. 2006; vander Windt et al., Cell Transplant. 2008; 17(9):1005-14), and they alsomay be transplanted in combination with sertoli cells, which have beensuggested to provide an immune suppressive effect in islet allografts(Yin et al., 2009 Transplantation. 2009 August 15; 88(3):339-45). In oneembodiment, a method of xenotransplantation is provided to transplantthe pancreatic cells provided herein into a primate wherein the isletsare administered by intraportal infusion. In one embodiment, a method ofxenotransplantation is provided to transplant the pancreatic cellsprovided herein into a primate wherein the islets are administered viathe intraperitoneal space, renal subcapsule, renal capsule, omentum, orvia pancreatic bed infusion.

The methods of the invention also include methods of xenotransplantationwherein the islets are encapsulated. The islets may bemicroencapsulated, macroencapsulated or a combination of both. All orsome islets may not be encapsulated. The materials used to producecapsules may be any known to one of skill in the art including, but notlimited to, nitrocellulose, alginate, acrylonitrile, agarose andpolytetrafluoroethylene. The capsule may be permeable or semipermeable.

Sufficient time to allow for engraftment (for example, 1 week, 3 weeks,and the like) is provided and successful engraftment is determined usingany technique known to one skilled in the art. These techniques mayinclude, but are not limited to, assessment of donor C-peptide levels,histological studies, intravenous glucose tolerance testing, exogenousinsulin requirement testing, arginine stimulation testing, glucagonstimulation testing, testing of IEQ/kg (pancreatic islet equivalents/kg)requirements, testing for persistence of normoglycemia in recipient,testing of immunosuppression requirements, and testing for functionalityof transplanted islets (See Rood et al., Cell Transplantation,15:89-104. 2006; Rood et al., Transplantation, 83:202-210. 2007; Dufraneand Gianello, Transplantation, 86:753-760. 2008; van der Windt et al.,2009, Am. J. Transplantation, 9(12):2716-2726. 2009).

One or more techniques may be used to determine if engraftment issuccessful. Successful engraftment may refer to relative to notreatment, or in some embodiments, relative to other approaches fortransplantation (i.e., engraftment is more successful than when usingother methods/tissues for transplantation). In some cases, successfulengraftment is determined by assessment of donor C-peptide levels. Whenporcine animals, tissues, cells are used, in one embodiment, engraftmentmay be considered successful when porcine C-peptide levels are aboutbetween 0.2-1.0 (ng/ml) or, more specifically, about between 0.2-0.65(ng/ml) (See Cooper and Casu, Xenotransplantation, 16:229-238. 2009;Rood et a!, Cell Transplantation, 15:89-104. 2006). In anotherembodiment, testing of IEQ/kg (pancreatic islet equivalents/kg)requirements is used. In this embodiment, fewer IEQ/kg are requiredrelative to that required using other methods/tissues fortransplantation. In some cases, the IEQ requirements may be belowapproximately 50,000 IEQ/kg of neonatal porcine mass or belowapproximately 25,000 IEQ/kg of adult porcine mass (Dufrane and Gianello,Transplantation, 86:753-760. 2008). In some cases, the IEQ requirementsmay be below approximately 100,000 IEQ/kg of adult porcine mass.Achieving blood glucose regulation with lower IEQ/kg levels may be oneindication of successful engraftment. In some cases, persistence ofnormoglycemia in the recipient (host) is a hallmark of successfulengraftment. A prolonged decreased (or no) dependence on exogenousinsulin for a period of time after the transplant is one indication ofsuccessful engraftment. This period of time may be for 3 months, 6months, 1 year, or greater than 1 year. It may follow a first transplantor may be measured from subsequent transplants. In some cases,successful engraftment is illustrated by a reduced need forimmunosuppression. This reduced need for immunosuppression may includethe lowering of a dose of one or more immunosuppressive drugs/agents, adecrease in the number of types of immunosuppressive drugs/agentsrequired, a shorter duration of immunosuppression, and/or lower or nomaintenance immunosuppression. In one embodiment, successful engraftmentmay be assessed by testing for functionality (partial or full) of thetransplanted tissue. This may include detecting donor C-peptide (forexample, porcine C-peptide) in combination with a greater than 50%reduction in exogenous insulin needs. In another example, functionalityof transplanted tissue may be defined as basal or stimulated C-peptidegreater than 0.3 ng/dl.

Further direction regarding islet cell transplantation may be found inthe following references: Bertuzzi et al., Cur Mol Med, 6(4):369-74.June 2006; Ricordi et al., Diabetes, 35:649. 1986; Korsgren et al.,Transplantation, 45:509. 1988; Dufrane et al., Xenotransplantation,13(3):204-14. May 2006; Toso et al., Cell Transplantation, 9:297. 2000;Cozzi and Bosio, Curr Opin Organ Transplant, 13(2):155-8. April 2008;Bottino and Cooper, Xenotransplantation, 15(2):104-6. March 2008.

A host in need of treatment or prophylaxis of diabetes can be a hostidentified as having diabetes, pre-diabetes or a diabetic relatedillness. The host can be suffering from: increased thirst or hunger, drymouth, frequent urination, unexplained weight loss, fatigue, blurredvision, headaches, loss of consciousness (rare), slow-healing sores orcuts, itching of the skin, frequent yeast infections, recent weightgain, velvety dark skin changes of the neck, armpit and groin, calledacanthosis nigricans, numbness and tingling of the hands and feet,decreased vision, impotency. Prediabetes, also known as “impairedglucose tolerance,” is a health condition with few symptoms but isalmost always present before a person develops the more serious type 2diabetes. More than 50 million people in the U.S. over age 20 haveprediabetes with blood sugar levels that are higher than normal, but arenot high enough to be classified as diabetes. To determine prediabetes,one of two blood tests is used—the fasting plasma glucose (FPG) test andthe oral glucose tolerance test (OGTT). During the FPG blood test, bloodsugar level is measured after an 8 hour fast. In the FPG test, ameasurement of 100 mg/dL-125 mg/dL indicates prediabetes and Greaterthan 126 mg/dL on two or more tests indicates diabetes. During the OGTTtest, blood sugar is measured after a fast and then again 2 hours afterdrinking a beverage containing a large amount of glucose. In the OGTTtest, a measurement of 140 mg/dL to 199 mg/dL indicates prediabetes anda measurement of greater than 200 mg/dL indicates diabetes.

EXAMPLES Example 1 Islet-Specific Expression Vector Construction

The mammalian expression vector pCI-Neo (Promega) sewed as a backdropfor the pancreatic islet-specific expression cassette. This vector wasmodified by a Clal excision of a 1967 base pair (bp) fragment containingthe phage fl region, the SV40enhancer and early promoter, the SV40minimum origin of replication, and the neomycin phosphotransferase gene.In addition, the CMV immediate-early enhancer/promoter was excised whenthe insulin-IT promoter was inserted into this vector using restrictionenzymes BglII and Hind III.

A choice of sequence to serve as the promoter element for the pancreasspecific expression vector was made by comparison of two clonedsequences amplified from the proximal sequence upstream of the ratinsulin II gene CDS. These amplified products varied in length from 497bp to 767 bp; the shortest amplified product most closely correspondedto that used previously in the literature. To determine which promotersequence amplimer was the best choice, the cDNA for GFP was introduceddownstream of each promoter sequence and these test vectors were usedfor transfection of Beta-TC-6 mouse pancreatic insulinoma cells. FACSanalysis was performed to test for transgene (GFP) expression intransfected cells. The analysis indicated that the longest amplimer (767bp) resulted in better expression of GFP; therefore all vectors used toproduce islet-specific expression contain this longest promoter element.The 767 bp region 5′ to the rat insulin II gene coding region wasamplified by PCR using purified high molecular weight rat DNA astemplate, PFx DNA polymerase (Invitrogen), and primers:

pins2bg 1 5′: gacgagatct accaaatcag gaacagaaag agtcpins2hd 3′: tatcaagctt acctgcttgc tgatggtttc cgac

This fragment serves as promoter in all vectors used to produce pigs andmice with pancreas specific expression of transgenes.

This rat insulin II (rins2) promoter region, as a BglIJIHindIIIfragment, was inserted into the ClaT-deleted pCI neo vector by digestionwith restriction enzymes BglII and Hind III, which at the same timeremoves the CMV enhancer promoter (765 bp frag) from pClneo.

The murine PDX-1 gene distal enhancer (483 bp) was amplified by PCRusing purified high molecular weight mouse DNA as template, PFx DNApolymerase, and primers:

muPDXbg 15′:  actgagatcttctagagagttcttctgtttgcta muPDXbam3′: gctcggatccttaaaggtaaatgaattttatata

The murine PDX-1 enhancer was inserted as a Bgl II/BamHI fragment 5′ ofthe rInsIT promoter in the BglII restriction site to create theintermediate pInsIT vector.

Multiple chicken 3-globin insulator fragments were inserted into thevector at locations flanking the enhancer/promoter/transgene site. Thechicken β-globin insulator (227 bp) was amplified by PCR using anin-house vector containing the insulator sequence, PFx DNA polymerase,and primers:

globins C1a5′: attaatcgatgggacagcccccccccaaag globins Xba3′:atattctagattttccccgtatccccccaggtgt globins Spe5′:attaactagtgggacagcccccccccaaag globins C1a3′:atatatcgatttttccccgtatccccccaggtgt

ClaI/XbaI insulator fragments and Spel/Clal insulator fragments weregenerated from this amplification and introduced into the Clal site atthe 3′ end of the pinsli vector containing the murine PDX-1 enhancer ina 3-fragment ligation. A total of 4 insulator fragments were introducedat this site.

Insulators for the 5′ end of the cassette were prepared by excising apair of insulator fragments from the vector containing the four 3′insulator fragments (above) with a Clal digest, blunting this Clalfragment with DNA polymerase I, large (Klenow) fragment, and insertingthis blunt-ended fragment into a blunted BglII site in the rInsIl vectoralready containing the promoter, enhancer, and 3′ flanking insulators.

This base vector is referred to as pREV788 and was used for allsubsequent introductions of transgenes for pancreatic islet-specificexpression. The vectors containing the introduced transgenes are shownin FIG. 1. The vectors utilized in the following examples are:

-   -   pREV788: The islet-specific vector cassette contains the rat        insulin II promoter with flanking chicken β-glob in insulators        and the murine PDX-1 enhancer. A multiple cloning site (MCS),        with an upstream chimeric intron and downstream SV40 pA signal,        is provided for transgene insertion and expression.    -   pREV790: A 184 lbp Xhol/Notl fragment containing the human TFPI        cDNA fused to cDNA coding for domains 3 and 4 of human CD4 and        the C-terminal sequence was inserted into the Xhol/Notl-digested        vector cassette.    -   pREV792: A 1637 bp Sall/Noti fragment containing the porcine        CTLA4 extracellular region cDNA, fused via a flexible linker to        the hinge CH2 and CH3 regions of human IgGi, was inserted into        the Sal l/Notidigested vector cassette.    -   pREV835: A 1609 bp Xhol/Xhol fragment containing the human CD39        eDNA was inserted into the Xhol-digested vector cassette.

Sequence for pCTLA4-Ig and TFPI are in part derived from sequencesdescribed in U.S. Pat. No. 7,432,344 and U.S. Pat. No. 6,423,316.

These vectors were transfected into two different primary porcine fetalcell lines (see Example 3). Cell line 183-6-6, was isolated from a malefetus that was genotype homozygous GTKO and heterozygous transgenic forCD46. Cell line 227-3 was isolated from a female pig (ear biopsy) thatwas homozygous GTKO and homozygous transgenic for CD46.

Transgenic mice were produced to test the pancreatic expression vector,with TFPI as the introduced transgene. Subsequently, pigs were producedwith demonstrated pancreas expression of CD39 (e.g. pig 320-2), and afetus was produced (548/A3) and subsequently recloned to produce pigswhich had demonstrated pancreas expression of both pCTLA4-Ig and TFPItransgenes (e.g pig 347-3). The pigs embodied in the following exampleswere all produced on a genetic background that was homozygous GTKO andCD46 transgenic (cell lines used were 183-6-6 or 227-3). Thus the genomeof these resulting pigs has three to four genetic modifications relevantto xenotransplantation, with at least one of these modificationsresulting in transgene expression specifically in the pancreas forutility in islet transplantation.

Example 2 Production of TFPI Transgenic Mice with Pancreas-SpecificExpression Vector pREV790

Zygote stage mouse embryos were obtained from 136C3 Fl females mated to136C3 Fl males (Harlan Sprague Dawley, Dublin, Va.). The females weresuperovulated with 7.5 IU PMSG (i.p., Calbiochem, San Diego, Calif.) and5.0 IU Hcg (i.p., Intervet, Millsboro, Del.) 44 to 48 h later. Zygoteswere collected and manipulated by standard methods (Hogan et al., 1994)in FHM (Specialty Media, Lavallette, N.J.). In vitro embryo culture wasdone in KSOM medium (Specialty Media) at 37° C. with 5.0% CO2 inhumidified air. Pronuclear microinjection of the pREV790 construct wasperformed using methods described previously (Page et al., 1995Transgenic Res. 4:12-17). Injected embryos were cultured in vitroovernight, at which time they were removed from KSOM and placed intoFHM. Viable two-cell embryos were transferred into the oviducts ofpseudo pregnant ICR mice (Harlan Sprague Dawley) using known techniques(Hogan et al., Manipulating the Mouse Embryo, 2nd edition, 2004) andallowed to deliver their pups naturally. At 21 days of age, pups wereweaned, sexed, and identified by toe notching. Tail tip biopsies werecollected for genotype analysis.

One-hundred twenty zygotes were microinjected, 87 were culturedovernight, and 76 resulting two-cell embryos were transplanted intopseudo pregnant recipients. Nineteen pups were born of which 4 werescreened by PCR and Southern analysis and found to be trans genic forthe pREV790 construct (21% transgenic rate). This transgenic rate iswithin the normal expected range using microinjection techniques.

Example 3 Cell Line Preparation for Nuclear Transfer Isolation of CellLines:

Two cell lines (183-6-6 and 227-3) were used as the genetic backgroundfor transfections to add the additional transgenes, and ultimately fornuclear transfer to generate pigs. Both cell lines were produced bybreeding of GTKO pigs (Dai et al., (2002) Nature biotechnology 20,251-255; Phelps et al., Science, (2003) 299:411-414) with ubiquitouslyexpressing hCD46 transgenic pig lines (Loveland et al.,Xenotransplantation, 2004, 11:171:183). Both cell lines were confirmedby genotype and phenotype as homozygous GTKO and hCD46 transgenic. Thecell lines were prepared for use in NT as follows: A fetal fibroblastcell line was isolated from fetus 183-6-6 at day 36 of gestation. TheFetus was mashed through a 60-mesh metal screen using curved surgicalforceps slowly so as not to generate excessive heat. The cell suspensionwas then pelleted and resuspended in DMEM containing 20% fetal calfserum and Antibiotic-Antimycotic (Invitrogen). Cells were cultured threedays, and cryopreserved.

An ear fibroblast cell line was isolated from a 48 day old pig (227-3)from an ear punch. The ear punch was washed with 200 proof ethanolfollowed by a wash with PBS. Tissue was minced with surgical scissorsand cultured for 12 days prior to cryopreservation. Fetus 548/A3 wascollected on day 73 of gestation, and pancreatic samples were isolatedfor expression analysis (Examples 6-7). In addition, fetal cells wereisolated (as described above) and banked for later recloning. (Example4).

Plasmidfragm Ent Preparation for Transfection:

pREV790 plasmid fragment was prepared for transfection by restrictionenzyme digestion with AatII and AhdI (New England Biolabs). pREV792 wasprepared by digestion with Asel and AatII (New England Biolabs). Theplasmid fragments generated by digestion were separated on a 1% low meltagarose gel (Cambrex) to remove the plasmid backbone. Thetransgene-containing cassette fragment of interest was excised andincubated twice in 2 volumes of 1× agarase buffer on ice for 15 minutes.After removing the buffer, the gel was melted at 65° C. 10 minutes.After 10 minutes at 42° C., 1 uL Agarase (New England Biolabs) per 100uL of gel melt and incubated minimum 1 hour at 42° C. One-tenth volumeof 3M Sodium Acetate was added to the gel melt and incubated on ice 15minutes. Centrifugation at 15000 rpm for 15 minutes at 4° C. separatesany undigested agarose. Two volumes of 100% ethanol were added to thesupernatant and centrifugation was used to pellet the DNA fragment. 70%ethanol was used to wash the pellet before drying at 37 C. The pelletwas resuspended in TE.

Transfection, Selection, Harvesting of Colonies for Screening:

Porcine ear fibroblasts from pig 227-3 were transfected with pREV790(PdxrInsII-hTFPI), pREV792 (Pdx-rInsII-pCTLA4-1g) and pREV828 (aPuromycin selectable marker gene vector). Approximately S million cellswere co-electroporated with 3jig of each of the transgene vectors and0.5 tg of the selectable marker vector. Forty-eight hours posttransfection, transfected cells were selected with the addition of 0.5mg/ml of the antibiotic Puromycin (InvivoGen, San Diego, Calif.) in20×10 cm dishes at a density of approximately 25,000 cells per dish.Media was changed 72 hours post initiation of puromycin selection.Colonies were harvested 7 days post initiation of selection. 70puromycin-resistant colonies were harvested and cultured further for 3days. Forty-five of 70 colonies grew and were split into two samples:one for PCR analysis and one for expansion. PCR analysis for bothpREV790 and pREV792 was performed as described in Example 5.Thirty-seven double-PCR positive colonies were pooled and cryopreservedfor future us in nuclear transfer.

Similar procedures were used for co-transfection, selection andharvesting of colonies using the pREV835 (Pdx-rInsII-CD39) vector, incombination with pREV828 and pREV792, except in this case cell line183-6-6 was used for transfection.

Example 4 Production of Multi-Transgenic Pigs by Nuclear Transfer (NT)

Various methods can be used to produce the multi-trans genic pigs of thecurrent invention. The following is one example in which donor cellsused (line 2273 and line 183-6-6) were the genetic background homozygousGTKO (lacked any function (xGT) and were also transgenic for CD46 (andexpressed CD46 in pancreas; FIG. 7). Donor cells were transfected,selected and screened positive for the pREV790, pREV792, and/or pREV835vectors, as described in Example 3, prior to being used for NT. In somecases, multiple colonies of transfected and selected cells, allscreening positive for the transgene(s), were pooled together prior totheir use in NT.

Donor cells (fetal or adult fibroblast cells) for NT were cultured inDulbecco's Modified Eagle Medium (DMEM, Gibco, cat#1 1995-065)supplemented with 10-20% fetal calf serum and 0-4 ng/ml basic fibroblastgrowth factor, in a humidified incubator at 5% 02, 5% CO2 balanced withnitrogen at 37 C. For culture, cells were seeded 3-7 days prior to thenuclear transfer procedure, at an appropriate dilution such that thecells would reach confluency 24-48 hours prior to nuclear transfer. Onthe day of nuclear transfer, donor cells were harvested about 30-45minutes before use in embryo reconstruction by using Trypsin-EDTA(Gibco, cat#25300-054), making a single cell suspension in suitableholding medium (e.g. Hepes buffered M199, Gibco cat #12350-039).

NT procedures were performed on in vitro matured oocytes (DesotoBiosciences, Christiansburg, Va.) using methods well known in the art(see, e.g., Polejaeva, et al., (2000) Nature 407, 86-90, Dai et al.,(2002) Nature biotechnology 20, 251-255, Campbell et al., (2007)Theriogenology 68 Suppl 1, S214-231, Vatja et al., (2007) Reprod FertilDev 19, 403-423). Electrical fusion and activation of reconstructedoocytes was performed using an ECM200 1 Electrocell Manipulator (BTXInc., San Diego). Fused and activated nuclear transfer embryos were heldin culture in phosphate buffered NCSU-23 medium (J Rprod Fertil Suppl.1993; 48:61-73) for 1-4 h at 38.5° C., and then transferred to theoviduct of an estrus-synchronized recipient gilt. Crossbred gilts (largewhite/Duroc/Landrace) (280-400 lbs) were synchronized as recipientanimals by oral administration of 18-20 mg Matrix (Altrenogest, Hoechst,Warren, N.J.) mixed into their feed. Matrix was fed for 14 consecutivedays. Human Chorionic Gonadotropin (hCG 1000 units; Intervet America,Millsboro, Del.) was administered intramuscularly 105 h after the lastReguMate treatment. Embryo transfers were performed by mid-ventrallaparotomy 22-26 h after the hCG injection. Pregnant Mare SerumGonadotropin (PMSG 1000 IIJ) and hCG (500 IU) we used on day 10 and 13post transfer for maintenance of pregnancy. Pregnancy was confirmed viaultrasonography 28 days post-transfer. Pregnancies were monitoredthereafter on a weekly basis. All piglets were born via naturalparturition.

Nuclear transfer using 183-6-6 cells which were puromycin selected andscreened positive for the pREV792 and pREV835 transgenes resulted inthree litters of piglets born to date; some piglets were genotypicpositive for both the pREV792 and pREV835 transgenes. One of thesepiglets, #320-2, was used for phenotypic analysis (see Example 7).Fibroblasts isolated from piglet 320-2 were also subsequently used fornuclear transfer (recloning) and have produced litters and liveoffspring.

Nuclear transfer using 227-3 cells which were puromycin selected andscreened positive for the pREV790 and pREV792 transgenes resulted in theproduction of fetus 548/A3, which was genotyped positive for both thepREV790 and pREV792 transgenes as well as the GTKO and CD46 geneticmodifications from the parent cell line. Cells isolated from fetus548/A3 were used for recloning and have produced seven litters to date(see Table 1). Piglet 347-3, from one lifter, was used for phenotypicanalysis in Examples 6-7. All of these recloned piglets were confirmedto have the same genotype as the 548/A3 fetus, i.e. they were transgenicfor the pREV790 (TFPI) and pREV792 (pCTLA4-1g) transgenes (pancreasspecific expression) and additionally were CD46 transgenic and GTKO (dueto the genetic background of the cell line used for transfection;227-3). To our knowledge, this is the first time pigs have been producedcomprising more than three genetic modifications. Table 1. Litters ofpiglets recloned from fetus 548/A3.

Litter ID Number Piglets Born (#) Viable Piglets*(#) 342  3  1 346  2  1347  5  5 367  2  2 371  2  2 375  2  2 384  2  2 TOTALS 18 15 *ViablePiglets are piglets born alive and viable for at least 24 hours. Somepiglets were euthanized at various ages for analysis of transgeneexpression or for other research studies. Two of these animals arecurrently being raised for breeding.

Example 5 Genotyping of Cells and Transgenic Animals by PCR and SouthernBlot Analysis Genotype Analysis:

Genomic DNA was extracted from transfected cells, and blood or tissuesamples from each mouse or piglet to be tested. In brief, tissue sampleswere lysed overnight at 60° C. in a shaking incubator with approximately1 ml lysis solution (50 mM Tris pH8.0, 0.15 MNaCl, 0.01 M EDTA, 1% SDS,25% Sodium perchlorate and 1% of 3-Mercaptoethanol and Proteinase K) per175 mg tissue. DNA was precipitated with isopropyl alcohol followingphenol/chloroform extraction. Resolubilized DNA was treated with RNase(1 mg/ml)+RNase Ti (1000 U/jil) at 37° C. for 1 hour, with proteinase K(20 mg/ml) at 55° C. for 1 hour, extracted with phenol/chloroform,precipitated and resuspended in Tris Ethylenedeaminetetraacetic acid(EDTA). DNA was isolated from whole blood samples using a DNA isolationkit for mammalian blood (Roche Diagnostics Indianapolis, Ind.).

For Southern blot analysis, about 10 μg of DNA was digested with theappropriate restriction enzyme (detail below) and separated on a 1%agarose gel. Following electrophoresis, the DNA was transferred to anylon membrane and probed with a 3′-end digoxigenin-labeled probe (probesequence below). Bands were detected using a chemiluminescent substratesystem (Roche Diagnostics, Indianapolis, Ind.).

pREV790—TFPI

The presence of integrated pREV790 construct was determined by PCR usingprimers 790.5L and 790.5R which target a 1000 bp fragment extending fromthe rat insulin II promoter into the 5′region of the TFPI codingsequence.

790.5L: agcaaagtccaggggtcag 790.5R: gaaatctggcttttcttgttgc

The presence of integrated pREV790 construct was confirmed by Southernblot analysis using a BamHI digest and probing with probe TFPIS′/3′.

TFPIS ′/3′ probe sequence:GGATTGTGTCGTGCCAATGAGAACAGATTCTACTACAATTCAGTCATTGGGAAATGCCGCCCATTTAAGTACAGTGGATGTGGGGGAAATGAAAACAATTTTACTTCCAAACAAGAATGTCTGAGGGCATGTAAAAAAGGTTTCATCCAAAGAATATCAAAAGGAGGCCTAATTAAAACCAAAAGAAAAAGAAAGAAGCAGAGAGTGAAAATAGCATATGAAGAAATTTTTGTTAAAAATATcTGcAgGAACCAGAAGAAGGTGGAaTTCAAAATAGACATCGTGGTGCTAGCTTTCCAGAAGGCCTCCAGCATAGTCTATAAGAAAGAGGGGGAACAGGTGGAGTTCTCCTTCCCACTCGCCTTTACAGTTGAAAAGCTGACGGGCAGTGGCGAGCTGTGGTGGCAGGCGGAGAGGGCTTCCTCCTCCAAGTCTTGGATCACCTTTGACCTGAAGAACAAGGAAGTGTCTGTAAAACGGGTTACCCAGGACCCTAAGC TCCAGATGGGCAAGAApREV792-pCTLA4-Ig

The presence of integrated pREV792 construct was determined by PCR usingprimers (792.s and 792.a) targeting a 473 bp fragment extending from therat insulin II promoter into the 5′ region of the CTLA4 coding sequence.The sequence of these primers was:

792.s:  cgctgtgggctcttctcttacat 792.a:  gagcaagccatggctaagcttaThe presence of integrated pREV792 construct was confirmed by Southernblot analysis using a BamHI digest and probing with probe792.s1792/a2265. 792s1792/a2265 probe seq:

CGCTGTGGGCTCTTCTCTTACATGTACCTTTTGCTAGCCTCAACCCTGACTATCTTCCAGGTCATTGTTCCAACaagcttTATTGCGGTAGTTTATCACAGTTAAATTGCTAACGCAGTCAGTGCTTCTGACACAACAGTCTCGAACTTAAGCTGCAGTGACTCTCTTAAGGTAGCCTTGCAGAAGTTGGTCGTGAGGCACTGGGCAGGTAAGTATCAAGGTTACAAGACAGGTTTAAGGAGACCAATAGAAACTGGGCTTGTCGAGACAGAGAAGACTCTTGCGTTTCTGATAGGCACCTATTGGTCTTACTGACATCCACTTTGCCTTTCTCTCCACAGGTGTCCACTCCCAGTTCAATTACAGCTCTTAAGGCTAGAGTACTTAATACGACTCACTATAGGCTAGCCTCGAGAATTCACGCGTGGTACCTCTAGAgtcgacGGTATCGATAAGCTTAGCCATGGCTTGCTC pRE′V835-CD39

The presence of integrated pREV835 construct was determined by PCR usingprimers CD3 9R3 and CD3 9L3 which targets a 584 bp fragment within theCD3 9 coding region.

CD3 9R3: CATAGAGGCGAAATTGCAGAG CD3 9L3: AGTATGGGATTGTGCTGGATG

The presence of integrated pREV835 construct was confirmed by Southernblot analysis using a Sad digest and probing with probe CD39L3/R3.

CD39 L3/R3 probe sequence:AGTATGGGATTGTGCTGGATGCGGGTTCTTCTCACACAAGTTTATACATCTATAAGTGGCCAGCAGAAAAGGAGAATGACACAGGCGTGGTGCATCAAGTAGAAGAATGCAGGGTTAAAGGTCCTGGAATCTCAAAATTTGTTCAGAAAGTAAATGAAATAGGCATTTACCTGACTGATTGCATGGAAAGAGCTAGGGAAGTGATTCCAAGGTCCCAGCACCAAGAGACACCCGTTTACCTGGGAGCCACGGCAGGCATGCGGTTGCTCAGGATGGAAAGTGAAGAGTTGGCAGACAGGGTTCTGGATGTGGTGGAGAGGAGCCTCAGCAACTACCCCTTTGACTTCCAGGGTGCCAGGATCATTACTGGCCAAGAGGAAGGTGCCTATGGCTGGATTACTATCAACTATCTGCTGGGCAAATTCAGTCAGAAAACAAGGTGGTTCAGCATAGTCCCATATGAAACCAATAATCAGGAAACCTTTGGAGCTTTGGACCTTGGGGGAGCCTCTACACAAGTCACTTTTGTACCCCAAAACCAGACTATCGAGTCCCCAGATAATGCTCTGCAATTTCGCCTCTATG

Example 6 Phenotypic Analysis (pCTLA4-1g) of Tissues from TransgenicPigs Western BlotforpCTLA4-Ig Expression:

Tissue and cell lysates were prepared by homogenization in the presenceof protease inhibitors (Thermo Scientific, Rockford, Ill.) followed bythe addition of SDS (1% final concentration) and centrifugation toremove residual cellular debris. Protein concentration was determinedwith a bicinchoninic acid (BCA) protein assay kit (Pierce, Rockford,Ill.). Heat-denatured and β-mercaptoethanol-reduced samples (10-20˜gprotein) were fractionated on 4-12% BisTris SDS gradient gels(Invitrogen, Carlsbad, Calif.). Recombinant human CTLA4-Ig/Fc (R&DSystems, Minneapolis, Minn.) was used as a standard control protein.Following electrophoresis, proteins were transferred to a nitrocellulosemembrane, stained with Memcode Protein Stain (Thermo Scientific) fortotal protein visualization, and blocked with casein-blocking buffer(Sigma-Aldrich., St. Louis, Mo.). The blocked membrane was incubated inrabbit anti-human IgG1-horseradish peroxidase (HRP) (The Binding Site,San Diego, Calif.), which recognizes the human IgG1 heavy chain regionof pCTLA4-Ig. Immunoreactive bands were detected with Super Signal WestPico Chemiluminescent Substrate (Thermo Scientific) and photographicimaging.

Fetus 548/A3, and a recloned piglet from 548/A3 cells (piglet 347-3)showed expression of the 56 kDa pCTLA4-Ig protein by Western,specifically in pancreas. (FIG. 2.)

Example 7 Phenotypic Analysis of Animals Expressing Transgenes inPancreas Histology and Immunofluorescence:

Mouse or pig Pancreata were removed and were either fixed in 10%formalin or frozen down in blocks of OCT (Electron Microscopy Sciences,Hatfield, Pa.). Formalin fixed tissues were blocked in paraffin and cutat 5 μm for staining with Hematoxylin and Eosin (H+E) staining. H and Estaining was performed using standard procedures. Frozen sections werecut at 5 μm on a cryostat and were stained with rabbit anti-human TFPI(polyclonal, American Diagnostica, Stamford, Conn., #4901), sheepanti-human IgG1 (polyclonal, The Binding Site, Birmingham, UK, #AUOO6),mouse anti-human CD46 (clone O.N. 137, mIgG2a, U.S. Biological,Swampscott, Mass.), mouse anti-human CD39 (clone BU6I, mIgG1, Ancell,Bayport, Minn.) or mouse anti-rat insulin/proinsulin (clone D3E7, mIgG1,Serotec, Oxford, UK). Isotype controls were run for rabbit IgG (JacksonImmunoResearch, West Grove, Pa.), sheep IgG (Jackson), mouse IgG2a(clone MRC OX-34, Serotec) and mouse IgG1 (clone MOPC-31C, BDPharmingen, San Jose, Calif.), respectively. Immunofluorescent (IF)staining was performed using a 3-step procedure. Frozen sections weredried and fixed in cold acetone (Sigma, St. Louis, Mo.), followed byavidin-biotin blocking (Invitrogen, Carlsbad, Calif.). Secondary Ab hostspecies serum blocking steps were also included (10% Donkey serum,Jackson). Primary Abs were diluted in PBS and incubations were performedfor 1 h at room temperature in a humidified chamber. The secondary Abused was biotinylated donkey anti-(rabbit, sheep, or mouse) IgG for 45mm and the tertiary Ab used was fluorescein-conjugated strep avidin for30 mm (Jackson). Slides were washed in PBS between steps, were coverslipped using 22×30 mm coverslips (VWR, West Chester, Pa.) and werepreserved using Slowfade with DAPI (Invitrogen). Representativehistological and IF pictures were taken using an Olympus DP71 camera ona Provis microscope, and analyzed using DP controller software (Olympus,Center Valley, Pa.) with a magnification of 200×.

Results:

pREV790 (TFPU Transgenic Mice:

One year old mice had very well clustered islets, as shown in therepresentative H+E histology. These mice expressed hTFPI in anislet-specific manner, staining was localized in a similar manner tothat of insulin (FIG. 3). hTFPI staining was more intense than insulin,indicating efficient islet-specific expression using the presentlydescribed system.

pREV790/pREV792 Transgenic Pigs:

Fetus 548/A3 was characterized by histology at 73 days of gestation(FIG. 4). Piglet 347-3 (a redone of 548/A3) was characterized at about2.5 months of age (FIG. 5). Beta cells are scattered and diffuse in afetal pancreata, which can be seen in the representative photos.Staining patterns for hTFPI and pCTLA4-Ig (hIgGI Ab) were similar toinsulin. Staining was more intense for hTFPI and pCTLA4-Ig than insulin.Piglet 347-3, at 2.5 months of age, had more developed islet clusters,and showed strong staining therein. The islet-specific expression inpiglet 347-3 was most intense for hTFPI, somewhat less intense forpCTLA-4-1g, and less intense for insulin.

pREV835 (CD39) Transgenic Pigs:

Piglet 320-2, at 3.5 months of age, had fully developed islet clusters,and showed strong staining for CD39 therein. The islet-specificexpression in 320-2 for hCD39 was more intense than for insulin, asshown in previous mouse and pig examples. (FIG. 6).

Example 8 Islet Isolation and In Vitro Coagulation Assays of TransgenicMouse and Pig Islets

Porcine and murine pancreatic islets can be isolated, cultured andtested in vitro for coagulation (clotting time), using laboratoryprotocols known in the art, examples of which are provided here.

Solutions for Islet Isolation and Culture:

25% Ficoll Stock solution:

-   -   33.3 g Ficoll 400, Type 400, Sigma #F-4375    -   100 ml HBSS/Hepes    -   Mix together with stirring and low heat until Ficoll goes into        into soln. Sterile filter. Store at 40 C. Make gradients from        the 25% soln.

For 50 ml: 25% Ficoll HBSS/Hepes   23% soln = 46 ml  4 ml 20.5% soln =41 ml  9 ml   11% soln = 22 ml 28 ml

-   -   Mix together thoroughly. Store at 40 C.

HB S S/Hepes:

-   -   500 ml HBSS with calcium and magnesium    -   10 ml Hepes 1 M    -   Mix together thoroughly. Store at 40 C.

HBSS/BSA:

-   -   500 ml HBSS with calcium and magnesium    -   10 ml Hepes 1 M    -   2.5 g BSA Fraction V    -   Filter sterilize after adding BSA. Mix together thoroughly.        Store at 40 C.

Collagenase:

-   -   1.95 mg Collagenase Type V Sigma #C-9263    -   1 ml HBSS/Hepes    -   Mix gently. Too much agitation will destroy enzyme action. Keep        at 40 C. Soln. is best used fresh but may be used for up to 3        days if kept at 40 C. Soln. gets weaker as it ages and may also        be frozen but activity is less after thawing.

Murine Islet Culture Media:

-   -   500 ml RPMI 1640    -   50 ml Fetal bovine serum (heat inactivated)    -   10 ml Hepes 1 M    -   5 ml Penicillin/Streptomycin (10,000 U/10,000 mg/ml)    -   5 ml L-glutamine (200 mM)    -   500 ul 2-Mercapto-ethanol 50 mM (stock: 0.2 ml in SSml PBS)    -   Filter sterilize and store at 40 C.

Mouse Islet Isolation Protocol:

Sacrifice mouse immediately before pancreas is harvested. Carry out theharvest and isolation procedure under sterile conditions in a flow hood.Perform a laparotomy and pull the skin and body wall back toward thehead. The liver will be reflected back against the diaphragm. Locate thecommon bile and follow to the juncture with the intestine. Place a clamparound the duodenum and over the end of the bile duct to prohibit flowfrom the bile duct into the intestine.

Fill a 3 ml or 5 ml syringe with cold collagenase soln. and attach a 30G needle. Bend the needle about halfway down the shaft to form a 90degree angle. Insert the needle into the bile duct, close to the liverwith the needle pointed toward the intestine. Slide the needle into thebile duct as far as possible without further damaging the duct (no otherpunctures) Inject the collagenase into the pancreas until it is fullydistended. Inject only a little at first making sure it is not leakinginto the intestine. If it is, readjust the clamp. Depending on the sizeof the animal, the inflation may take 2-5 ml collagenase. After pancreasinflation, remove needle and clamp. The pancreas is removed by tearingand cutting away from the attached tissue and ducts. For maximum yield,remove the entire pancreas. Wash the excised pancreas in coldcollagenase soln, then placed in a 25 cm2 flask and kept on ice untilall other pancreata are harvested. No more than 4 pancreata are placedin one flask. Place an additional 1-2 ml in the flask before incubation.Incubate the flask at 370 C for 18-20 minutes without shaking.

After incubation, shake the flask sharply for about 10 seconds or untilthe tissue is homogenous. Stop the action of the enzyme by adding 10 mlcold HBSS-BSA to the flask. Replace the cap and shake the flask againsharply for 2-3 more seconds. Pour the tissue slurry into a 50 mlconical tube and fill to 50 ml with HBSS-BSA. Mix, then let gravitysettle for 5 minutes. This is done to remove the fine particles oftissue that are not islets. The islets are large and will fall to thebottom without centrifugation. Remove the supernatant without disturbingthe loosely settled pellet. Mix the pellet by pipetting or shaking andwash again. Repeat washing step 2-5 times until the supernatant isrelatively clear. The amount of washing depends on the size of tissueused. Chunks of undigested tissue may be removed by passing the tissuethrough a wire 20 mesh screen during the second or third wash.

After the last wash, resuspend the pellet at the rate of 5 ml HBSS-BSAper pancreas. The digested tissue is divided and placed into 17×100 mm(14 ml) round bottom polystyrene tubes. No more than 2 pancreata are putinto a tube. Gently centrifuge the tubes at 1000 RPM for 1 minute topellet the tissue. Remove as much of the supernatant as possible fromthe pellet so as not to dilute the Ficoll gradient. Add 4 ml of the 25%Ficoll soln to the tube and resuspend the tissue by vortexing for 5-10seconds. Overlay the remaining Ficoll gradients (2 ml of each) startingwith 23%, 20.5% and finally 11%. Do not disturb or mix the layers orinterfaces. Centrifuge tubes at 1800 RPM for 10 minutes.

After centrifugation, the islets are mostly at the interfaces betweenthe 11 & 20.5% layers and between 20.5 & 23%. Take all the layers andinterfaces separately and put them into 15 ml conical tubes. Examineevery layer for islets before discarding. Wash the layers with HBSS-BSAonce. Centrifuge for 1 minute at 1000 RPM. Remove supernatant by pipet.Wash once more in complete media and let gravity settle for 3-5 minutes.Remove supernatant by pipet. Do not disturb the loose pellet. Collectwhat is left in the tube and place in a 60 mm non-tissue culture sterilePetri dish. Islets are now ready to hand-pick and count.

Pig Pancreas Digestion with Collagenase:

Prepare the collagenase (Liberase PT or Collagenase P, Roche). Prepare asolution of HBSS with 1 mg/collagenase/ml. Keep on ice until ready touse. Prior to use it warm to 24° C. For the entire pancreas of an adultpig make up 500 ml of solution.

-   1. On a sterile bucket on ice, clean the pancreas from connective    tissue, fat, blood.-   2. Take the organ out of ice.-   3. Locate the pancreatic duct (if using the entire pancreas) then    inject collagenase through the duct. Alternatively, for partial    organ samples or if the duct cannot be located, inject collagenase    directly in the parenchyma.-   4. Injection can go on for up to 5 minutes.-   5. Cut the organ into pieces (½ inch each) and put into a beaker    with more pre-warmed collagenase (enough to cover the entire    piece/s).-   6. Place in a 37° C. waterbath and continue to shake manually.-   7. After a few minutes the tissue will start to break up. The entire    piece may not digest. Avoid overdigestion of the cells that are    released, therefore after 10 minutes of shaking, if the solution is    getting cloudy, begin to recover the free cells with a pipette and    transfer the cells to a bottle or beaker (on ice) with abundant cold    RPMI solution containing serum (5%).-   8. Continue the warm digestion until enough cells are collected, but    don't expose the tissue for longer than 30 minutes to the warm    collagenase.-   9. Wash the cells in cold RPMI+serum several times to remove the    collagenase.-   10. Centrifuge at 1000 RPM for 3 minutes.-   11. To obtain isolated islets, run a ficoll gradient.-   12. For small amounts of tissue pellet, use 50 ml conical tubes.-   13. Make density gradients of: stock 1.132, layers 1.108, 1.096,    1.037.-   14. Load 2 ml of pellet dispersed in 10 ml of stock Ficoll on the    bottom. On top 8 ml of 1.108, 8 ml of 1.096. 8 ml of 1.037, and 5 ml    of HBSS.-   15. Centrifuge 20 minutes at 800 g or 2000 rpm.-   16. The islets should be at the second and third interface, but    check other layers to be sure.-   17. Wash out ficoll very well (at least 3 washes for 3 minutes at    1200 rpm, with RPMI+serum), then culture or fix the cells as needed.

Protocol for In Vitro Coagulation (Clotting Time) Assay: Materials

-   -   CMRL-1066 medium (Gibco/Invitrogen, Carlsbad, Calif.) at 37 C    -   Incubator shaker at 37 C    -   Polystyrene untreated 24 well plates    -   Pipettes    -   1 mL syringes    -   Vacutainer set: needle, rubber band,    -   Alcohol swaps    -   Band aid    -   Container for trash    -   Timer

Method

-   -   Plate 100 handpicked islets in 200 uL CMRL medium at 37 C per        well    -   Plate 200 uL CMRL medium at 37 C in control wells with blood        only    -   Add 200 uL freshly drawn human blood to each well.    -   Mix gently by shaking the plate and place plate in incubator        shaker    -   Observe the experiment for coagulation times

Islets were isolated using methods such as those detailed above. Normalwild-type (WT) mouse or pig islets were used as controls. Islets werealso prepared from a TFPI-transgenic mouse line (pREV790; see Example2). The TFPI transgenic pig islets were obtained from the 548/A3 pigline described in Example 4. Islets were mixed with freshly isolatedhuman blood and coagulation time was determined for clot formation. Thein vitro coagulation times (in minutes) for transgenic mouse and pigislets exposed to human blood (two separate experiments), are shown inTable 2 below:

Sample Experiment One Experiment Two Control 28.27 >30.00 (human blood -no islets) Mouse Pig (pREV790) (pREV790/pREV792)* Wild Type Islets  8.054.30 Transgenic Islets 10.24 6.12 *The pig sampled was also GTKO andCD46 transgenic.

Expression of the transgenes in islets lead to a 33% increase inclotting time in mouse islets, and a 38% increase in clotting time inpig islets.

Example 9 Determination of In Vivo Functionality of a Transgenic PorcineIslet Xenograft in Non-Human Primate (NHP) Transplantation Induction ofDiabetes and Immunosuppression in NHP:

In a non-human primate model, diabetes can be chemically induced using arecently-developed streptozotocin protocol as adapted for cynomolgousmonkeys, and diabetic state and donor islet survival/function can bemonitored using insulin and primate-specific and porcine-specificC-peptide assays (Rood et al. 2006, Casu et al 2008, Bottino et al.2009).

A co-stimulatory blockade drug, human CTLA4Ig, with similar activity ashuman anti-CD 154mAB, can be used in combination with ATG inductiontherapy, and maintenance therapy with MMF. CTLA4-Ig is currently apotential alternative to CD 154mAB, that has already been used by onegroup for pig-to-nonhuman primate islet Tx (Cardona et al., 2006). ThisCTLA4Ig (Orencia) can be administered at 12.5-25 mg/kg i.v. at the sametime intervals as anti-CD 154mAb (days −1, 0, 4, 7, 10, 14, 19, andweekly, to maintain a trough level >300 ng/ml) to STZ-induced diabeticmonkeys. This dosing regimen, in combination with ATG and MMF, wasdemonstrated, in preliminary studies, to be sufficient to preventsensitization in baboons that received a GTKO pig artery graft(Ezzelarab et al, manuscript in preparation).

-   -   In summary, immunosuppression of NHP for islet transplantation        can be as follows: Induction:        -   Anti-thymocyte globulin (ATG) 1-10 mg/kg i.v.×2 (days −3 and            −1) to reduce the T cell count to <500 cells/mm3 on day 0.    -   Maintenance:        -   Mycophenolate mofetil (MMF) 50-100 mg/kg/day p.o. to            maintain 12-hour whole blood trough levels at 3-bug/ml        -   CTLA4-Ig 25 mg/kg i.v. on days −1, 0, 4, 7, 10, 14, and then            weekly.

Porcine Islet Preparation and Transplantation:

Pig islet isolation is carried out shortly after removal of the pancreasfrom anesthetized pig donors. Porcine islets are obtained using amodification of the semi-automated method described by Ricordi, usingspecific collagenase blends designed for swine, lower digestiontemperature, gentle injection of enzyme and virtually no mechanicalshaking (Bottino et al., 2007). Purification of the islets is achievedby centrifugation on a cell processor machine (COBE 29911) ondiscontinuous gradients (Bottino et al., 2007, 2009). Functionalproperties and viability of the isolated islets are evaluated for eachislet batch. In the absence of a non human primates model of autoimmunetype 1 diabetes, hyperglycemia is induced by the i.v. injection ofstreptozotocin (STZ, Zanosar, 125-150 mg/kg). Vascular lines inserted inthe carotid artery and jugular vein of the monkeys, and connected to thetether system, allow easy access for drug delivery and blood drawing andpermit optimal i.v. insulin administration following diabetes induction.Intravenous glucose tolerance tests (IVGTT) and arginine stimulationtests (AST) are carried out before and after streptozotocinadministration to confirm the diabetic status, and after thetransplantation, to evaluate the graft response to secretagogues. On theday of transplantation, islets, following overnight culture in CMRL-1066medium supplemented with 10% Heat-Inactivated Fetal Calf Serum, 10 mMNicotinamide, 2 mM glutamine and Pen-Strepto, are counted, resuspendedin CMRL containing 4 mg Dextrane Sulphate to prevent coagulation, andinjected in the portal vein by gravity over a period of 5-10 minutes.Porcine C-peptide release, an indicator of islet cell destruction, ismeasured after one and two hours after islet infusion and a peakindicates the degree of initial islet cell loss due to IBMIR. Historicaldata accrued from previous experiments, can be used to evaluate theability of the transgenes to prevent early islet loss. Serum C-peptideconcentrations are determined using specific porcine and humanantibodies that do not cross react with each other, making it possibleto distinguish between endogenous and graft insulin production followingxenotransplantation (Casu et al. 2008).

The early loss of islets from IBMIR can be monitored by (i) measurementof the C-peptide levels within the first 24 hours (as a marker of isletdestruction), (ii) the blood glucose level, (iii) exogenous insulinrequirement post-Tx (as indicators of the success of the transplant inmaintaining a state of normoglycemia), (iv) presence of numerous viableislets (insulin-positive) in the liver, and (v) extent of cellularinfiltration of the graft on histologic examination after necropsy.

Example 10 In Vivo Function of CD46 Transgenic Pig Islets in DiabeticMonkeys

To determine the utility of the CD46 expressing cells for treatment ofdiabetes in a primate, diabetes was chemically induced in cynomolgousmonkeys as described in Example 9.

hCD46+ pig islet donors were derived by outcrossing from a progenitorline carrying the hCD46 transgene, a minigene under control of itsendogenous promoter. Ubiquitous hCD46 expression was observed byimmunofluorescent microscopy of all tissues analyzed and of isolatedislets (Loveland et al., Xenotransplantation, 2004, 11:171:183).Diabetes was induced and confirmed in 9 monkey recipients as describedin Example 9. Group A recipients (n=4) were transplanted with eitherwild-type porcine islets (n=2) or islets isolated from GTKO pigs (n=2),in numbers of 85,000 to 100,000 IEQ/kg of body weight. Group Brecipients (n=5) received equal numbers of islets from hCD46+ pigs. Twogroup B animals were retransplanted after 49 and 91 days, respectively.Immunosuppression was identical for both groups and consisted ofantithymocyte globulin for induction, anti-CD 154 monoclonal antibodiesand mycophenolate mofetil (MMF). Monkeys were followed until loss ofgraft function, or up to 3 months after transplant, except for one groupB animal that was allowed >1 yr of follow-up.

Functional porcine islet survival, determined by detectable porcineC-peptide in combination with a more than 50% reduction of exogenousinsulin needs, was achieved in all monkeys. In group A, islet survivallasted for 7, 20, 31, and 46 days. In group B, the use of hCD46+ isletssignificantly prolonged functional porcine islet survival to the full 3months or beyond yr of follow-up, respectively (log-rank test P=0.0042).Post-transplant weekly fasting porcine C-peptide levels were comparablefor groups A and B during the first 45 days (1.10±0.41 versus 1.19±0.88ng/mL, student t-test P=0.860). After 45 days, C-peptide positivity wasmaintained at 0.87±0.41 ng/mL only in group B recipients.

Insulin independence was achieved in 3 of 4 Group A monkeys for a periodof 5, 17, and 36 days, respectively. Four of 5 group B monkeys becameinsulin independent for 87, 9192, and >396 days, respectively. Duringtimes of insulin independence, fasting blood glucose values were wellcontrolled (group A: 91±18 mg/dL; group B: 112±22 mg/dL, student t-testP=0.250). None of the monkeys recovered endogenous beta cell function.

Histological evaluation of post-transplant livers revealed many viableporcine islets in group B animals. T cell infiltration was successfullyprevented. Serum levels of anti-Gal and/or anti-nonGal antibodies didnot increase in group A, nor group B monkeys, nor after re-transplant.Nevertheless, 1 gM, IgG, and C4d was seen on engrafted islets byhistological analysis of group A livers, but only to a minimal extent onislets in group B livers.

With CD46 as the only transgene, large islet doses were still required(75,000100,000 IEQ/kg), and there was still significant early graft lossassociated with the hCD46 xenograft. In addition, the exogenousimmunosuppression regime utilized is not amenable to use in humanpatients (see van der Windt et al., Am. J. Transplantation,9(12):2716-2726. 2009).

Example 11 Phenotype of pCTLA4-Ig Expressing Pigs

Although the development of pCTLA4-Ig expressing animals has beensuggested, these animals are severely immunocompromised. Pigs expressingCTLA4-Ig ubiquitously using a CAG enhancer/promoter were found to havean immunocompromised phenotype and were not viable in a typicalhusbandry environment.

Primary fetal fibroblasts (originating from Landrace/Duroc/Large Whitecrosses) from WT or GTKO pigs were co-transfected by electroporationwith a 10:1 ratio of linearized pCTLA4-Ig construct to either apgkpuromycin^(r) or pgkncomycin^(r) vector. At 48 h, cells were seededin 48-well plates at a concentration of 100-500 cells/cm², and selectedwith either 250 μg/ml G418 (Gibco BRL, Grand Island, N.Y.) or 0.5 μg/mlpuromycin (InvivoGen, San Diego, Calif.). Selected clones were screenedfor the pCTLA4-Ig transgene by polymerase chain reaction (PCR), andpositive clones (8 with WT background, 70 with GTKO background) werepooled and used for nuclear transfer. These cells were subject tonuclear transfer as described above. Animals were farrowed in segregatedhousing to minimize exposure to pathogens and received feed containingtetracycline (110 g/kg of feed) starting at birth and continuing untileuthanasia. pCTLA4-Ig expression was assessed via western blot andimmunofluorescence showing robust expression. Serum concentrations ofpCTLA4-Ig were high, ranging from approximately 380 to 1,600 μg/mlserum.

The pCTLA4-Ig transgenic pigs and non-transgenic littermates appearedhealthy for a period of approximately 2 months. At that point, thetransgenic piglets began showing signs of illness, including fever,general malaise, abnormal hair growth, and, in some cases, skin lesions.In the WT/pCTLA4-Ig pigs, which had been weaned from the sows (theirmothers) and housed in the whole-herd nursery these illnesses were acuteand, after symptoms became evident death rapidly resulted. Mosttransgenic pigs succumbed to illness or required euthanasia by 10-11weeks of age. Non-transgenic littermates in these litters remainedhealthy. Hematological analyses indicated that, without prophylactictreatment, transgenic pigs, in contrast to their non-transgeniclittermates, had low white blood cell (WBC) counts, ranging from 53% to71% of normal values. Total lymphocyte counts were also subnormal inthese animals, ranging from 14% to 61% of normal values.

The CAG-pCTLA4-Ig transgenic pigs produced on a homozygous GTKObackground, developed a more chronic illness and, despite antibiotictreatment, the health of these pigs continued to deteriorate and, atapproximately 10 weeks of age, the last of these pigs was euthanized.The 4 non-transgenic littermates, raised with their CTLA4-transgenicsiblings, remained healthy and vigorous (see: Phelps et al.,Xenotransplantation, 16(6):477-485. 2009).

Example 12 Production of Pig Containing Five Genetic Modifications(GTKO, CD46, and Pancreatic Islet Specific TFPI, CTLA4-Ig and CD39)

Transfection of cells from fetus 548/A3 (genetic modifications:homozygous GTKO/CD46/TFPI/CTLA4-1g) was performed to add the pREV835(CD39) transgene. Fetal fibroblasts were transfected with the pREV835transgene using procedures similar to those described in Example 3.Ninety-nine colonies were harvested and screened for the presence of thepREV835 transgene using procedures described in Example 5. Cells fromten positive colonies were pooled and prepared for use in nucleartransfer. Nuclear transfer was performed using the pooled pREV835positive cells as nuclear donors and following procedures described inExample 4. Embryos were transferred to 4 recipient gilts, and 2pregnancies were established. Ten pigs were born; four of these pigswere born alive. Genotypic analysis indicated that three of the fourlive born pigs contained the pREV835(CD39) transgene in addition to thefour genetic modifications from the 548/A3 line(GTKO/CD46/TFPJICTLA4-1g). To our knowledge, this is the first time pigshave been produced comprising more than four genetic modifications.

Example 13 Fertility of Multi-Transgenic Pigs and Stable Transmissionand Co-Segregation of Multiple Transgenes to Offspring when aMulti-Transgenic Pig was Bred Naturally

Natural breeding of female pig 347-2 (a pig produced by NT using 548/A3donor cells) to a homozygous GTKO male pig, resulted in a normalpregnancy and a litter of eleven pigs born, thus demonstrating fertilityof this multi-transgenic animal. Five of these pigs were born alive. Twoof the live born pigs carried the two additional islet specific (548/A3line) transgenes transmitted from their dam (TFPI and CTLA4-1g) as wellas the GTKO and CD46 genetic modifications inherent to the parent cellline. The other three offspring were positive for GTKO and CD46 only.The table below summarizes the genotype of the 347-2 offspring(determined by Southern analysis).

Genotype (as determined by Southern analysis) TFPI CTLA4-Ig Animal GTKOCD46 (pREV790) (pREV792) Dam (347-2) (+) (+) (+) (+) Sire (+) (−) (−)(−) Offspring 417-1 M (+) (+) (+) (+) 417-2 M (+) (+) (−) (−) 417-3 F(+) (+) (−) (−) 417-4 F (+) (+) (+) (+) 417-5 F (+) (+) (−) (−)Southern analysis indicates that all animals transgenic for TFPI arealso transgenic for CTLA4Ig; this suggests that the TFPI and CTLA4-Igtransgenes co-integrated in the porcine genome, co-segregated duringmeiosis, and were transmitted together via breeding. Resulting offspringproduced by breeding the 548A3 line carry either the two islet specifictransgenes together, or neither islet specific transgene. Fluorescent insitu hybridization (FISH) analysis of offspring animal 417-4 is underwayto further analyze this co-integration. In this analysis, probes forCTLA4Ig and TFPI will be labeled with distinctive fluorescent tags andhybridized with chromosomal DNA. Hybridization of both probes at asingle locus will indicate that these transgenes co-integrated and willbe inherited together in future generations of pigs. Animal 417-4 isbeing raised for future breeding as well.

Example 14 ATPase Functional Assay of CD39 Positive Porcine Islet Cells

Isolation of Porcine Islets from Pig 390-1:

Pancreatic tissue was obtained from animal 390-1, a pig with fivegenetic modifications produced in Example 12. The pancreas was trimmedof fat and injected with cold HMS+O.Smg/ml of Collagenase P (RocheApplied Science, Indianapolis, N). The pancreas was warmed to 37 C for30 minutes. It was then placed in cold HBSS and the organ was teasedapart using forceps. Dispersed tissue was run through a mesh screen (30mesh) to remove large pieces of tissue. Pancreatic islets were purifiedusing an Optiprep™ (Axis-Shield, Oslo, Norway) protocol. The tissuepellet was resuspended in 20 ml RPMI and 10 ml of Optiprep workingsolution (final concentration 1.1 g/ml) Eight ml of 1.085 Optiprep™ wasoverlaid followed by 10 ml of RPMI. The tubes were spun at 500×g for 5minutes at 4 C. Islets present in the top interface were removed and asample was stained to confirm presence of islets. Islets were plated ina 96 well plate in preparation for ATPase assay.

ATPase Assay on 390-1 Islets:

CD39 is an extracellular enzyme which catalyzes ATP and ADP to AMP (thusliberating phosphate). Therefore an ATPase chromogenic assay(QuantiChrom™ ATPase/GTPase Assay Kit, BioAssay Systems (Hayward,Calif.), which measures the liberation of phosphate, was used todetermine functionality of the CD39 transgene in porcine islets, ascompared to islets isolated from a wildtype pig. Fetal fibroblasts froma pig with high level ubiquitous expression of CD39 (animal 325.1) wereused as a positive control.

Cells were diluted to provide confluency in a row of wells of a 96-wellplate, with a 1:10 dilution in a second row of wells. All cells receivedone wash with Tris buffered saline (TBS). Cells were frozen overnight,thawed, and the contents of 6 confluent wells were pooled and suspendedin a final volume of 100 ul TBS. This volume was split (SOul/ea) into 21.5 ml Eppendorf tubes. To each tube was added:

90 ul 2× sample diluent1.8 ul 100 mM ATP (final 1 mM concentration) or H₂O

38.2 ul H₂O

The reaction mix was incubated with shaking at 37 C for 30 minutes, andthen centrifuged at 8000 rpm. Ten ul of the supernatant was mixed with190 ul H₂O (1:20 dilution). An 80 ul volume of this dilution was addedto the first row of wells on a 96 well plate. Two-fold serial dilutionswere made down the columns of wells for dilutions from 1:20 to 1:2560.Phosphate dilutions (0-50 uM) were prepared and added to the plate toserve as a standard curve. Malachite green reagent (200 ul) from theATPase kit was added to each well and the plate was incubated at roomtemperature for 45 minutes. Readings at OD620 were performed andconcentrations of released phosphate were determined by interpolationfrom the phosphate standard curve.

As shown in FIG. 8, islets from pig 390-1 had higher levels of releasedphosphate than wildtype islets, indicating functionality of theexpressed CD39 transgene.

Example 15 Immunofluorescence of Pancreatic Tissue from Multi-TransgenicPig

Samples of pancreatic tissue were collected from piglet 390-1 atapproximately 3 months of age (genotype: GTKO, CD46, TFPI, CTLA4-Ig andCD39 transgenic) and phenotypically characterized by IF as described inExample 7. Strong staining was present for all transgenic proteins inpancreas: CD46, TFPI, CTLA4-Ig, and CD39 (FIG. 9); notably in the isletcell component. Insulin staining of islets in the tissue examined isalso shown. Expression of TFPI, CTLA4-Ig and CD39 was islet-specific andwas not seen in other tissues/organs tested (not shown) All isotypecontrols stained negative (not shown).

What is claimed is:
 1. A transgenic animal that lacks any expression offunctional alpha 1,3 galactosyltransferase (GTKO) and specificallyexpresses at least one transgene in pancreatic tissue.